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[accumulators] Offer to help with maintenance
by Cromwell Enage 29 Jun '19

29 Jun '19

Hi, everyone! I'm offering to help maintain Boost.Accumulators and have already e-mailed Eric Niebler regarding my intentions. With the deadline for Boost release 1.71 fast approaching, I can take steps to ensure that Boost.Accumulators is in a usable state. I also have a few ideas on how to update and improve Boost.Accumulators (one of them being to make use of variadic templates), but they can wait until after the release for further discussion. Very respectfully, Cromwell D. Enage

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Re: [boost] [logic] Boost::logic (tribool?) actively developed?
by Jacob Lidman 28 Jun '19

28 Jun '19

> It has resently updated to support a change in gcc compilers. So I > would say it's actively maintained. I never asked if it was actively maintained but rather if the library is actively developed, i.e. are new features added, improvements in documentation... > I would say it seems stagnant because it's always been as close to perfection as a > library can be. The reason why the library appear close to perfect is because it clearly has minimal number of features. Improvements can be made to accommodate new needs, e.g. by including other logics. > see https://github.com/boostorg/logic As I mentioned this is the repo for the tribool library, at least that was the name prior to boost 1.70.0

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Some out_ptr concerns
by Glen Fernandes 28 Jun '19

28 Jun '19

Thanks to JeanHeyd for going through the Boost review process, and to Zach for managing the review. Briefly: I do not have enough reasons to recommend acceptance for out_ptr just yet --- in its current form. (I'd like to see it return for a new review when the feedback from this review shapes the design so that some of these concerns are resolved). Second: This excludes "inout_ptr" (for which I had even more concerns) and just focusing on "out_ptr" - which is the simpler and more common use case of the two. Below comparing out_ptr vs the hand written code that a user would write to use a /typical/ C out-pointer API with smart pointers, this is what I'm comparing: [Typical code user would write]: Type* raw; Result result = TheCApi(args..., &raw); if (!Success(result)) { // failure (e.g. return, or branch and handle error) } Smart<Type, Deleter> smart(raw, etc...); [What happens with out_ptr now]: /* 'smart' already has to exist here before TheCApi is called. Either as Smart<Type, Deleter> smart; or Smart<Type, Deleter> smart(nullptr, etc...); depending on deleter */ /* User writes: Result result = TheCApi(args..., out_ptr(smart)); // or Result result = TheCApi(args..., out_ptr(smart, etc...)); depending on deleter */ Type* raw = nullptr; Result result = TheCApi(args..., &raw); if (raw != nullptr) { smart.reset(raw); // or smart.reset(raw, etc...); depending on deleter } if (!Success(result)) { // failure (e.g. return, or branch and handle error) } Concern 1. Having to materialize the smart pointer before TheCApi is called. Ordinarily this might be fine for some smart pointers and stateful deleters, but it may not be for others. Concern 2. The original user code initializes the smart pointer based on Success(result). The out_ptr version would do so based on whether the raw out pointer was changed to something non-null by TheCApi. This might be fine for some cases, but it may not be for others. That it isn't the same as fundamental logic as the user code bothers me, though. Concern 3. The equivalent of the hand written user code is less overhead. Personally I'm of the opinion that maybe this doesn't matter too, but here the author does say he has users who cannot abide by it, and that this facility needs support from e.g. std::unique_ptr to be viable. (And this leads to concern 4 below). [I'm not a fan of needing unique_ptr implementations to add support for this to make it comparable to some user's hand written code]. Concern 4. The UB optimization that the author wrote because of Concern 3 is a real concern to him. The UB optimization has no place in Boost, and one of which doesn't even work with many C++ library vendors' unique_ptr. [Fortunately the Boost reviews have already echoed this sentiment and I believe this is going away]. Concern 5. Supporting other custom smart pointers requires effectively re-implementing out_ptr_t by specialization. I have come to see this as not viable. [Already mentioned in other reviews] Concern 6. C APIs where the deleter (its state, logic, etc.) are governed by some other result from TheCApi. This is can be worked around in many cases, but the workaround is clumsy. Or insupportable, in other cases. i.e. The stateful deleter is always initialized with 'etc...' either before-hand via Smart<Type> smart(nullptr, etc...) or at call site with: TheCApi(args, out_ptr(etc...)); before analyzing other results of calling TheCApi. (The 7th concern I had made notes about pre-review has already been eliminated, when the unconditionally noexcept destructor is now only conditionally noexcept). Other thoughts: The suggestion by Emil lead to an interesting alternative idea to this problem domain, but I had no time to fully explore it. I don't think it would address all of these concerns. It has some other greater appeal, e.g. a way to call C APIs that materializes the smart pointers as results (along with C API return value) of an "Invoke-style" thing. Or even a way to transform a C API with out-pointers into a C++ callable that returns smart pointers (along with C API return value) via a "Bind-style" thing. Glen

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out_ptr -- alternatives
by Andrzej Krzemienski 28 Jun '19

28 Jun '19

Hi Everyone, This is not a review of out_ptr, but I wanted to share my thoughts about the motivation for this library. I do not recall any time from my programming experience where I was in need of passing a smart pointer to a T** interface, so maybe this is why I cannot appreciate the value of out_ptr. On the other hand, if I need to use a library with a C API, or other non-C++ API (this happens when someone wants to naively port a Java library to C++ and keep the Java interface) the first thing I do is to wrap the API functions into a RAII class. It takes some time up front, but then whenever it is used, I do not have to deal with the problems of the old API. `T**` is only one of the problems. The motivation focuses on only easily passing smart pointers to `init(T**)` functions, but it does not address the problem of adapting the error reporting of `init(T**)`to the error reporting of my program. I would never want to only solve the former problem and omit the latter. Also, I would never want to represent a handle to a resource with a smart pointer, as I do not want to voluntarily inject the null-pointer state that I now have to take care of everywhere. Instead I would prefer a dedicated type that is not default-constructible, where one really needs to try hard to get the special no-resource state (e.g. by moving from and not destroying the object). What I am missing from the motivation of out_ptr is the comparison with a full RAII wrapper solution. You can argue that the scope of out_ptr is just different: provide interpoperation between `init(T**)`functions and smart pointers. But I would argue that this latter goal is wrong. In fact, I am concerned that we might be encouraging a bad programming style: "need to work with init(T**) APIs? use shared_ptr." instead of promoting RAII wrappers that directly wrap the resource. Does anyone else feel the same? Or am I missing something about the problem domain? Anyway, I think that this problem should be covered in the documentation. Regards, &rzej;

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[logic] Boost::logic (tribool?) actively developed?
by Jacob Lidman 27 Jun '19

27 Jun '19

Hi, Is boost::logic actively developed and if so what are the future plans for the library? >From the source/documentation it seems to be dormant since ~2004 and a renaming of the tribool package. The latter is listed as a library on the boost homepage but lack a library repo on github.com/boostorg (?). BR /Jacob

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ASIO TCP connection switch
by JH 27 Jun '19

27 Jun '19

Hi, I have an application using ASIO TCP/IP SSL socket connection in an embedded device, the device has two network interfaces, when one is down, another network interface takes over, which requires application TCP SSL socket connection to be established binding to a new network interface. What will be an appropriate implementation to switch application TCP connection from one to another interface? Option 1: Restart application Option 2: Terminate the old interface socket, create a new socket to start initial connection Option 3: Some reconnection method which I don't know Appreciate you advice. Thank you. Kind regards, - jupiter

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Can boost ASIO socket binding to any interfaces or support QUIC?
by JH 27 Jun '19

27 Jun '19

Hi, I posted a similar question in another email but title was not appropriate, let me try it here using a more accurate clear title. I might need separate it into email questions, I am not quite clear it is boost socket nature or it is NAT issue. I have both client server applications using boost asio TCP socket, the client application is a Linux embedded system IoT device installed in home connect to server via NAT, the embedded system has two network interfaces, WiFi and cellular, in anytime there is only one network interface is up ans signed by an IP address, when one interface is down, another interface is up and signed IP address. The problem for an existing TCP socket connection is it cannot change from one interface to another. When one interface down another interface takes over, the client application continual sends data to the down interface buffered in TCP queue without transmission error but the server would never receive the data. It seems the only solution is to use QUIC, hence I asked here if there is any boost functions to support QUIC I can replace the TCP socket by QUIC. Appreciate your advice and tips. Thank you. Kind regards, - jupiter

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[build] Build errors with gcc - bad argument -mcpu=v7
by Andrey Semashev 26 Jun '19

26 Jun '19

Hi, I'm trying to run tests for Boost.Core with the following command: bjam -j 8 toolset=gcc cxxstd=14 variant=release libs/core/test Compilation fails with the following errors: gcc.compile.c++ bin.v2/libs/core/test/lightweight_test_fail10.test/gcc-8/release/cxxstd-14-iso/threading-multi/visibility-hidden/lightweight_test_fail10.o g++: warning: ‘-mcpu=’ is deprecated; use ‘-mtune=’ or ‘-march=’ instead cc1plus: error: bad value (‘v7’) for ‘-mtune=’ switch cc1plus: note: valid arguments to ‘-mtune=’ switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client icelake-server bonnell atom silvermont slm knl knm intel x86-64 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 btver1 btver2 generic native "g++" -std=c++14 -fvisibility-inlines-hidden -fPIC -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -mcpu=v7 -DBOOST_ALL_NO_LIB=1 -DNDEBUG -I"." -c -o "bin.v2/libs/core/test/lightweight_test_fail10.test/gcc-8/release/cxxstd-14-iso/threading-multi/visibility-hidden/lightweight_test_fail10.o" "libs/core/test/lightweight_test_fail10.cpp" ...failed gcc.compile.c++ bin.v2/libs/core/test/lightweight_test_fail10.test/gcc-8/release/cxxstd-14-iso/threading-multi/visibility-hidden/lightweight_test_fail10.o... I'm not sure where that -mcpu=v7 comes from, but I don't have it in my options, nether do I see it in the Jamfile.

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[release] 1.71.0 closed for new libraries and breaking changes
by Michael Caisse 26 Jun '19

26 Jun '19

The master branch is now closed for new libraries and breaking changes, and will be closing for major changes in a week and closed for the beta in two weeks. Also, if you're ready, you can also add your libraries' changes to the release notes at: <https://github.com/boostorg/website/blob/master/feed/history/boost_1_71_0.q…> Thanks, -- The Boost Release Team

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Boost 1.54 build integration errors in VS2017
by nunna, sarath babu (GE Healthcare) 26 Jun '19

26 Jun '19

HI, I am getting below error when I tried to integrate boost 1.54 version into our project using VS2017. error C3861: 'assert_arg': identifier not found error C2039: 'assert_arg': is not a member of 'boost::mpl' I am not able to fix this error. Hence, Please provide me help to get rid of this error. Thanks, Sarath.

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IP TCP connections asio::ip::tcp::socket
by JH 25 Jun '19

25 Jun '19

Hi, I am running an application using boost ASIO IP/TCP socket to connect Internet. I have two network interfaces, when one is down, it switches to another one, in my application

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[boost-ci] Added support for building big-endian on Travis CI
by James E. King III 24 Jun '19

24 Jun '19

You can now run a big-endian build job on Travis CI through some docker magic. I had an endian bug in some relatively new code in Boost.UUID (in the MD5 hasher) that required a big endian environment to build in and test with, so I had to solve this impediment. The Boost Docker Development Environment (BDDE) was taught how to build and run multiarch images. At this point I'd like to consider having BDDE move into boostorg alongside boost-ci. It provides an easy way to hop into or run boost builds inside docker containers. One of the examples is to run a predef unit test in the arm64 or ppc64 containers and see how predef defines the macros. Following that, Boost-CI was taught how to use BDDE under Travis CI to run a build in one of the containers. When running the red-ppc64 image expect a slowdown in the 10x to 20x range. If you are concerned about build time on Travis CI (maximum length 50 minutes), I would recommend running a subset of tests. Even building b2 (bootstrap) takes more than a minute. Building Boost.UUID with tests takes about 25 minutes (this includes building some of Boost.Serialization). You can also use BDDE directly to build the same way on a docker-enabled development system. I wasn't able to run gdb in this environment when the architecture was ppc64, but I could build and run tests. gdb works on the x86_64 docker container. Boost-CI: https://github.com/boostorg/boost-ci BDDE: https://github.com/jeking3/bdde Example PR that enables it on Travis CI: https://github.com/boostorg/uuid/pull/109 Enjoy, - Jim

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Serialization Issue found in 1.69 and 1.70 of boost libraries
by nunna, sarath babu (GE Healthcare) 24 Jun '19

24 Jun '19

Hello, We use boost libraries in our project. We had no issues found in 1.47 version in our product.(In Windows 7) But we wanted to upgrade to latest version into Windows 10 environment. We have got issues with serialization. Please let us know in which version you have introduced serialization above than 1.47 version? So that we will take one version below than that or let us know whether have to include/modify anything to adopt latest 1.69 or 1.7 version of boost. Your response will be a great help to us. Thanks, Sarath.

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[build] Option to have b2 show stdout from target run?
by James E. King III 24 Jun '19

24 Jun '19

Currently b2 only shows output when a test fails unexpectedly. If I want to build and run a test and see the stdout from the test all in one command, is there a b2 option that would do that? For example, the output from predef's "info_as_cpp" test is useful, and I'd like to have a single command line that builds it, runs it, and shows stdout. I don't see a way to do this with b2, even with the -d+n flags. I can do it this way, but it's fragile: $(b2 -a -ox info_as_cpp | grep 'gcc.link' | cut -d' ' -f2) - Jim

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B2 release 4.0.0
by Rene Rivera 24 Jun '19

24 Jun '19

After even more years of development the landscape of build systems has changed considerably, and so has the landscape of compilers. This version marks the start of B2 transitioning to a C++ implementation. Initially this means that the engine will be compiled as C++ source but that source is still the base C implementation. Over time it will transform to a C++ code base in both the engine and build system. Some changes in this start: - Requires C++ 11 to build engine. - Simplified build scripts to make it easier to maintain. - Building with C++ optimizations gives an immediate performance improvement. *Other changes in this release:* - Add support for using prebuilt OpenSSL. -- *Damian Jarek* - Define the riscv architecture feature. -- *Andreas Schwab* - Add ARM64 as a valid architecture for MSVC. -- *Marc Sweetgall* - Set coverage flags, from coverage feature, for gcc and clang. -- *Damian Jarek* - Add s390x CPU and support in gcc/clang. -- *Neale Ferguson* - Support importing pkg-config packages. -- *Dmitry Arkhipov* - Support for leak sanitizer. -- *Damian Jarek* - Fix missing /manifest option in clang-win to fix admin elevation for exes - with "update" in the name. -- *Peter Dimov* - Add freertos to os feature. -- *tee3* - Default parallel jobs (-jX) to the available CPU threads. -- *Rene Rivera* - Simpler coverage feature. -- *Hans Dembinski* - Better stacks for sanitizers. -- *James E. King III* *WARNING*: The default number of parallel jobs has changed in this release from "1" to the number of cores. There are circumstances when that default can be larger than the allocated cpu resources, for instance in some virtualized container installs. *Continuously tested on:* - Linux Clang 3.5, 3.6, 3.7, 3.8, 3.9, 4, 5, 6, 7, 8 - Linux GCC 4.7, 4.8, 4.9, 5, 6, 7, 8, 9 - macOS Xcode 8.3.3, 9.0, 9.0.1, 9.1, 9.2, 9.3, 9.3.1, 9.4, 9.4.1, 10.0, 10.1, 10.2, 10.2.1 - Windows MinGW 8.1.0 - Windows VS 2013, 2015, 2017, 2019 Documentation and more at <https://boostorg.github.io/build/> -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net

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Re: [boost] [Boost-testing] Test Failures on develop
by Tom Kent 24 Jun '19

24 Jun '19

On Fri, Jun 21, 2019 at 5:11 AM Tom Kent <lists(a)teeks99.com> wrote: > > > On Thu, Jun 20, 2019, 10:35 PM Rene Rivera <grafikrobot(a)gmail.com> wrote: > >> On Thu, Jun 20, 2019 at 10:28 PM Tom Kent <lists(a)teeks99.com> wrote: >> >>> >>> On Thu, Jun 20, 2019 at 7:15 AM Rene Rivera <grafikrobot(a)gmail.com> >>> wrote: >>> >>>> Since it's not due to the b2 -j change.. >>>> >>>> On Fri, Jun 14, 2019 at 8:25 AM Tom Kent via Boost-Testing < >>>> boost-testing(a)lists.boost.org> wrote: >>>> >>>>> For the last few days (Since June 4?) I've been having problems with >>>>> all my linux tests running against the develop branch. >>>>> >>>>> GCC ends with this: >>>>> >>>>> gcc.compile.c++ ../../bin/common/build/gcc-8/release/process_jam_log.o >>>>> >>>>> "g++-8" -fPIC -O3 -finline-functions -Wno-inline -Wall >>>>> -DBOOST_ALL_NO_LIB=1 -DNDEBUG -D_CRT_SECURE_NO_WARNINGS - >>>>> I"/var/boost/run/boost_root" -c -o >>>>> "../../bin/common/build/gcc-8/release/process_jam_log.o" >>>>> "../../common/build/../src/p >>>>> rocess_jam_log.cpp" >>>>> >>>>> ../../common/build/../src/process_jam_log.cpp: In function >>>>> 'std::__cxx11::string {anonymous}::revision(const string&)': >>>>> ../../common/build/../src/process_jam_log.cpp:359:16: warning: >>>>> ignoring return value of 'int system(const char*)', decla >>>>> red with attribute warn_unused_result [-Wunused-result] >>>>> std::system("git rev-parse --short=6 HEAD >.short-sha"); >>>>> ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>>>> ...skipped <p../../bin/testing/build/gcc-8/release>process_jam_log for >>>>> lack of <p/var/boost/run/boost_root/bin.v2/libs/f >>>>> ilesystem/build/gcc-8/release/link-static/visibility-hidden>libboost_filesystem.a... >>>>> >>>>> >>>> >>>> I guess you'd need to find out what it says for trying to build >>>> filesystem lib. >>>> >>> >>> Here's what I'm seeing with the filesystem error: >>> >>> ln -f -s >>> "../../libs/detail/include/boost/detail/has_default_constructor.hpp" >>> "../../../boost_root/boost/detail/has_ >>> default_constructor.hpp" >>> >>> gcc.compile.c++ >>> /var/boost/run/boost_root/bin.v2/libs/filesystem/build/gcc-8/release/link-static/visibility-hidden/path_traits.o >>> >>> "g++-8" -fvisibility-inlines-hidden -m64 -O3 -finline-functions >>> -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL >>> _NO_LIB=1 -DBOOST_FILESYSTEM_STATIC_LINK=1 -DNDEBUG >>> -I"/var/boost/run/boost_root" -c -o "/var/boost/run/boost_root/bin. >>> v2/libs/filesystem/build/gcc-8/release/link-static/visibility-hidden/path_traits.o" >>> "/var/boost/run/boost_root/libs/file >>> system/src/path_traits.cpp" >>> >>> /var/boost/run/boost_root/libs/filesystem/src/path_traits.cpp:20:10: >>> fatal error: boost/filesystem/config.hpp: No such f >>> ile or directory >>> #include <boost/filesystem/config.hpp> >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> compilation terminated. >>> ...failed gcc.compile.c++ >>> /var/boost/run/boost_root/bin.v2/libs/filesystem/build/gcc-8/release/link-static/visibility-hidden/path_traits.o... >>> gcc.compile.c++ >>> /var/boost/run/boost_root/bin.v2/libs/filesystem/build/gcc-8/release/link-static/visibility-hidden/portability.o >>> >>> "g++-8" -fvisibility-inlines-hidden -m64 -O3 -finline-functions >>> -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL >>> _NO_LIB=1 -DBOOST_FILESYSTEM_STATIC_LINK=1 -DNDEBUG >>> -I"/var/boost/run/boost_root" -c -o "/var/boost/run/boost_root/bin. >>> v2/libs/filesystem/build/gcc-8/release/link-static/visibility-hidden/portability.o" >>> "/var/boost/run/boost_root/libs/file >>> system/src/portability.cpp" >>> >>> /var/boost/run/boost_root/libs/filesystem/src/portability.cpp:20:10: >>> fatal error: boost/filesystem/config.hpp: No such f >>> ile or directory >>> #include <boost/filesystem/config.hpp> >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> compilation terminated. >>> ...failed gcc.compile.c++ >>> /var/boost/run/boost_root/bin.v2/libs/filesystem/build/gcc-8/release/link-static/visibility-hidden/portability.o... >>> >>> >>> And several more like that. >>> >>> However, I'm also suspicious of the timing with the processor change. >>> >>> Looking back at the last successful builds of develop on linux. I have a >>> few from linux/x86_64/docker machines. The last one I saw was building with >>> gcc-8 on June 4 around 6:30am CDT. There should have been a successful >>> clang run about 5hrs after that (11:30am CDT), and another successful gcc >>> around 10hrs after the last one that was actually successful (4:30pm CDT). >>> >>> This seems like it would correspond to the change to build here: >>> >>> https://github.com/boostorg/build/commit/451059949d92b52b21f802562a50587f1e… >>> >>> The other failure I started seeing was only my linux/arm64 machine. This >>> doesn't run docker, so might not be affected in the same way. The last >>> successful run on there was at 4:50pm CDT on June 4...but it typically >>> takes around 9hrs to run so it probably got the pre 451059949 commit. >>> However here I can't rule out that it was impacted by a8ab76ef973. >>> >>> I'm going to try to standup some normal VMs soon and run on them to see >>> if they are affected in the same way. It would also be nice if we could try >>> backing out the usage of _SC_NPROCESSORS_ONLN and see if that fixes things, >>> is that feasible to try for a couple days? >>> >> >> Again.. It's not a b2 issue. Specifying the "-jX" option entirely >> obviates the changed code. It's almost certainly something else. Places to >> look would be in the filesystem lib, or the root "boost" project for >> changes. >> > > Looking at regression.py it looks like the command that builds > process_jam_log doesn't use the bjam options. Can you verify if this > is/isn't the case? > > Tom > Somewhere between 9:57am and 12:02pm CDT today this bug migrated to master. It can trivially be re-produced. On a bare linux vm...Azure F8s_v2, Ubuntu 18.04, standard SSD. $ sudo apt update && sudo apt install build-essential gcc-8 g++-8 python python3 git wget ... $ wget https://raw.githubusercontent.com/boostorg/regression/develop/testing/src/r… $ echo using gcc : 8 : g++-8 : \; > ~/user-config.jam $ python run.py --runner=teeks99-test01 --toolsets=gcc-8 --tag=develop --bjam-options="-j8 address-model=64" ...fails with the above errors. You can also do the same thing to reproduce in a docker image (ubuntu:bionic). --bjam-options of -j1 -j8 and absent all fail the same. This does not correspond to any changes between the filesystem library that indicates the error. But it *does* correspond exactly with the release of the new B2. https://github.com/boostorg/build/commit/04efaac148671479b514db882b1c520dca… There have been no successful regression tests by any linux runners since that time. Tom

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Release tags request..
by Rene Rivera 24 Jun '19

24 Jun '19

B2 is doing it's own "out of band" (aka independent) releases. In order to avoid confusion.. Can the Boost release process please avoid tagging the build subrepo with the Boost release tags from now on? -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net

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[boost-users] [compiler] Boost VC++ 14.2 test compiler
by Alex J 23 Jun '19

23 Jun '19

Hi, Does anybody know when VC++ 14.2 will be added as a 'primary compiler tested' ?. At the moment there is only VC++ 14.1. Thanks

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Travis CI again.
by John Maddock 23 Jun '19

23 Jun '19

Sorry, but I need help, and simply can not see what's going wrong with: https://github.com/boostorg/config/pull/286. Travis doesn't even seem to be building the same code as has been pushed? And until I can get CI functioning again here, and in other libraries, nothing gets merged to master :( Sorry if I'm being dense, and thanks in advance, John. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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[release] 1.71.0 deadline for new libraries approaching
by Michael Caisse 22 Jun '19

22 Jun '19

One week from today master will closed for new libraries and breaking changes. Thanks, -- The Boost Release Team Boost Calendar with the release schedule: <http://www.boost.org/development/index.html>

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[process][type_erasure] Including both process and type_erasure creates duplicate definitions in mp11 and fusion
by Jared McIntyre 21 Jun '19

21 Jun '19

I've found that type_erasure::any and process::child conflict with each other in how they use mp11 and fusion. The issue may be specific to compiling the process library on Windows as it occurs in calls through detail headers in the library that are specific to Windows, and I haven't tested on other platforms.. #include <boost/type_erasure/any.hpp> #include <boost/process/child.hpp> Order doesn't matter. 1>c:\<removed>\boost\boost\fusion\adapted\std_tuple\tag_of.hpp(38): error C2953: 'boost::mpl::sequence_tag<std::tuple<_Types...>>': class template has already been defined 1>c:\<removed>\boost\boost\mp11\mpl.hpp(155): note: see declaration of 'boost::mpl::sequence_tag<std::tuple<_Types...>>' Boost 1.67, 1.70 VS 2017 (5.9.12)

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[boost-developers] [MSVC142] When is boost going to add MSVC 14.2 as a test compiler
by Alex J 21 Jun '19

21 Jun '19

Hi, I can see that boost has updated their code to support MSVC14.2 builds. However according to latest 1.70 docs, they are not testing on 14.2 compiler. When can we expect boost to include 14.2 as one of their primary test compilers ? Thanks Alex

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Re: [boost] [release] 1.71.0 deadline for new libraries approaching
by Kenneth Porter 20 Jun '19

20 Jun '19

Can we get this fix into the crc library? It fixes a warning in MSVC compilers. <https://github.com/boostorg/crc/pull/2>

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CMake config scripts broken in 1.70
by Alexander Grund 19 Jun '19

19 Jun '19

Hi all, I discovered a severe logic flaw in the generated CMake Config files for the new Boost 1.70 which make them almost unusable. As an example the static variant contains: if(NOT"${Boost_USE_STATIC_LIBS}"STREQUAL""ANDNOTBoost_USE_STATIC_LIBS) _BOOST_SKIPPED("libboost_filesystem.a""static, Boost_USE_STATIC_LIBS=${Boost_USE_STATIC_LIBS}") return() endif() if(BUILD_SHARED_LIBS) _BOOST_SKIPPED("libboost_filesystem.a""static, BUILD_SHARED_LIBS=${BUILD_SHARED_LIBS}, set Boost_USE_STATIC_LIBS=ON to override") return() endif() The shared variant contains: if(NOT"${Boost_USE_STATIC_LIBS}"STREQUAL""ANDBoost_USE_STATIC_LIBS) _BOOST_SKIPPED("libboost_filesystem.so.1.70.0""shared, Boost_USE_STATIC_LIBS=${Boost_USE_STATIC_LIBS}") return() endif() if(NOTBUILD_SHARED_LIBS) _BOOST_SKIPPED("libboost_filesystem.so.1.70.0""shared, BUILD_SHARED_LIBS not ON, set Boost_USE_STATIC_LIBS=OFF to override") return() endif() Although the message text says otherwise the 2nd return in both cases depends solely on BUILD_SHARED_LIBS. I'm pretty sure the intention was too check for BUILD_SHARED_LIBS *only* if Boost_USE_STATIC_LIBS is not set (see thread https://lists.boost.org/Archives/boost/2019/02/245030.php) As can be seen this is not the case. I haven't found the repo which contains the code that generates this so I can't report it there or fix it myself. As the issue here makes using Boost 1.70 (almost) impossible (in Scenarios like BUILD_SHARED_LIBS=ON (a CMake variable influencing the project build) and Boost_USE_STATIC_LIBS=ON) I'd recommend fixing this and pushing out a bugfix release. Regards, Alexander Grund

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Re: [boost] [Boost.Config] Detect compiler support for std::current_exception
by dariomt＠gmail.com 19 Jun '19

19 Jun '19

> > >>> 2) How can I test proper support for std::current_exception() and > >>> std::rethrow_exception() if exceptions are disabled for the test? > >> > >> You should probably condition your test on BOOST_NO_EXCEPTIONS and make > >> the test no-op when exceptions are disabled. > > > > But that defeats the whole purpose of having tests. > > Not really. You would still test the facilities when exceptions are > enabled. OTOH, I don't see why would anyone care about these components > when exceptions are disabled. > > If the Jamfile disables exceptions for the library tests, then I think I need to care. Otherwise this config macro would be untested. > > I think I should at least use the type std::exception_ptr, and make sure > > the functions std::current_exception() and std::rethrow_exception() exist > > (even if I cannot test that they actually work as expected at runtime). > > > > I think the following should work, and at least the test tests something > > when exceptions are off: > > > > using std::exception_ptr; > > auto current = &std::current_exception; > > auto rethrow = &std::rethrow_exception; > > > > What do you think? > > If it works, that would be fine by me. I don't disable exceptions and I > don't know whether the standard library components related to exceptions > stay available when exceptions are disabled. I wouldn't be surprised if > they don't (now or in a future version of the standard library > implementation). In any case, as I said, I don't see anyone using these > components when exceptions are disabled, so not much point in testing. > > In the end I settled for using std::exception_ptr; using std::current_exception; using std::rethrow_exception; because some old version of clang had issues with auto, sigh... The problem now is that something else is broken in the CI tests, but I'm quite confident that the tests should pass in all of msvc, gcc, clang I'd like to ask for the PR #285 to be merged into develop please ( https://github.com/boostorg/config/pull/285) Thanks!

1 0

Ticket #9804 - polygon intersection
by Michael Knafo MTH 19 Jun '19

19 Jun '19

Hello ! I have encountered the same problem described in bug #9804: "The result of an intersection is sometimes equal to one of the input polygons, when the result should be empty". https://svn.boost.org/trac10/ticket/9804 Does anyone knows if this bug was fixed and in which boost version ? Is there any version release notes related to this bug ? Alternatively, does anybody know what cause this problem ? Thanks Michael *********************************************************************************************** Please consider the environment before printing this email ! The information contained in this communication is proprietary to Israel Aerospace Industries Ltd. and/or third parties, may contain confidential or privileged information, and is intended only for the use of the intended addressee thereof. If you are not the intended addressee, please be aware that any use, disclosure, distribution and/or copying of this communication is strictly prohibited. If you receive this communication in error, please notify the sender immediately and delete it from your computer. Thank you. Visit us at: www.iai.co.il

2 2

Proposed for inclusion in boost: a C++11 span
by Hans Dembinski 17 Jun '19

17 Jun '19

Dear all, I started to work on a C++11 implementation of std::span. The interface will be an exact mirror of std::span, https://en.cppreference.com/w/cpp/container/span. Having a drop-in replacement of std::span for systems with older compilers in Boost seems like a very good idea. Is anyone else already working on this? I am happy to join forces. Coding down the span took me an hour, but several more hours will go into unit testing and documenting. Best regards, Hans

3 4

Re: [boost] [Boost.Config] Detect compiler support for std::current_exception
by dariomt＠gmail.com 17 Jun '19

17 Jun '19

> > > > > However, in my test I throw and catch exceptions: > > But the CI jobs have gcc and clang configured to compile without > exception > > support! > I have two questions: > > > > 1) Where are exceptions disabled in the CI jobs? I can't find it in > > the .travis.yml, > > but I can see e.g. clang being invoked with -fno-exceptions > > It's in the test/Jamfile.v2 file, look for <exception-handling>off. > Thanks! > > > 2) How can I test proper support for std::current_exception() and > > std::rethrow_exception() if exceptions are disabled for the test? > > You should probably condition your test on BOOST_NO_EXCEPTIONS and make > the test no-op when exceptions are disabled. > But that defeats the whole purpose of having tests. I think I should at least use the type std::exception_ptr, and make sure the functions std::current_exception() and std::rethrow_exception() exist (even if I cannot test that they actually work as expected at runtime). I think the following should work, and at least the test tests something when exceptions are off: using std::exception_ptr; auto current = &std::current_exception; auto rethrow = &std::rethrow_exception; What do you think?

2 1

CI: clang installation broken in current Travis build images
by John Maddock 17 Jun '19

17 Jun '19

Currently, pretty much all attempts at installing clang on the travis build images is failing: https://travis-ci.org/boostorg/config/builds/546084433?utm_source=github_st…. And since all the boost libraries have pretty much copied each others .travis.yml files, this means that most PR's for most libraries will be failing. Anyone any ideas? Thanks, John. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

3 2

[boostrap.bat] compilation error
by Raffi Enficiaud 16 Jun '19

16 Jun '19

I have the following during the compilation of bootsrap/b2: d:\bamboo_build_dir\rs-bcb233-vc2008win\library\tools\build\src\engine\sysinfo.h(41) : error C2864: 'b2::system_info::cpu_core_count_' : only static const integral data members can be initialized within a class d:\bamboo_build_dir\rs-bcb233-vc2008win\library\tools\build\src\engine\sysinfo.h(42) : error C2864: 'b2::system_info::cpu_thread_count_' : only static const integral data members can be initialized within a class Current develop (yesterday), Raffi

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[Range] pr for bug in any_range / development/maintenance status
by Max Jendruk 14 Jun '19

14 Jun '19

Hello everyone, I submitted a bugfix on Github about a month ago that fixes an issue where passing a (non-reference) value type as Reference parameter to any_range could lead to undefined behaviour. The issue has been known for a while (5 years). I would like to know when I can expect this to be merged. Also, is there a general review cycle that I'm not aware of? There are still a couple of other pull requests open, some of which were opened over a year ago. Just by looking at the activity on Github, it's difficult to determined how actively Boost.Range is still being maintained. What is the development/maintenance status of the library? I'm wondering whether it would be worth the time implementing a few more adaptors similar to those in the C++20 standard like take_view, join_view, and all_view, which I'd be happy to do. Are additions to the library still being accepted at this point? Best regards, Max

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[regression tests] Regression test pages not updating since June 4th
by Joaquin M López Muñoz 11 Jun '19

11 Jun '19

Thank you, Joaquín M López Muñoz

1 0

[out_ptr] Review scheduled for June 16 to June 26
by Zach Laine 10 Jun '19

10 Jun '19

This is a heads-up that out_ptr has been scheduled for review, starting next Sunday, June 16. From JenHeyd's earlier post about the library: " Documentation: https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr.adoc Repository: https://github.com/ThePhD/out_ptr <https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr.adoc> Standards Proposal: https://thephd.github.io/vendor/future_cxx/papers/d1132.html boost.out_ptr is a library for making it easy to interoperate between smart pointers and traditional C-style initialization and allocation interfaces. It also enables doing so in a way that allows library authors to opt into speed optimizations for their smart pointers that give them performance equivalent to typical C pointers (see benchmarks ( https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr/benchmarks.adoc) and the Standard C++ proposal for more details). " Please consider checking out the library now, and doing a review next week. It's a pretty small library; reviews should be pretty quick to do. Zach

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Re: [boost] [Boost.Stringify] Yet another formatting library.
by Roberto Hinz 09 Jun '19

09 Jun '19

On Sat, Jun 8, 2019 at 9:53 AM Helmut Zeisel <HZ2012(a)gmx.at> wrote: > Actually I did not check your library, but I would be interested in a > formatting library that is not based on functions, but on function objects. > > The usage would not be something like > > std::string s1 = to_string("base10", 15); > std::string s2 = to_string("base16", 42); > > but > > stringifier dec; > dec.set_base(10); > std::string s1=hex(15); > stringifier hex; > hex.set_base(16); > std::string s2=hex(42); > > To format values in Boost.Stringify, one does like this, for example: namespace strf = boost::stringify; int v = 255; std::string s = strf::to_string(v, " in hexadecimal is ", strf::hex(v)); assert(s == "255 in hexadecimal is ff"); So could maybe lambdas solve your need ? auto hex = [](int v){return strf::to_string(strf::hex(v)); }; auto dec = [](int v){return strf::to_string(v); }; auto s1 = hex(15); auto s2 = dec(42); assert(s1 == "f"); assert(s2 == "42"); > With a function object based interface, one could easily store and reuse > different formating options in parallel. > Not clear to me what you mean by that. Could you explain better ?

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[Boost.Stringify] Yet another formatting library.
by Roberto Hinz 08 Jun '19

08 Jun '19

Dear Boost Community, Naturally, any interest in a new formatting library must be lower now that fmtlib is approved into C++20. Still, I'm confident that the library I'm working on has great potential, so I would like to know your opinions. https://github.com/robhz786/stringify This is a locale-independent formatting library that: - has great performance ( almost twice as fast as fmtlib ) - can do things that others can't, like encoding conversion. - is highly customizable. Through "facets" you can specify things like numeric punctuation, encoding error handling, and the width calculation algorithm. - is highly extensible. Not only you can add new input types with own formatting options and facets, but also easily add new output types. The doc has an example of how to extend the library to write to QString ( from Qt ). Actually, I did announce this library about two years ago. But the design is much enhanced now. I believe it will be ready for review by the end of this year. But it may take longer. I much appreciate any feedback. Thank you. Roberto

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Setting up linter for boost library development
by Sagnik Dey 07 Jun '19

07 Jun '19

If someone has a linter setup with appropriate settings, can you please share details? I'm working on Boost.Real and would like to have a linter to help with coding style consistency. Help is appreciated. Thank You

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Re: [boost] [Boost.Config] Detect compiler support for std::current_exception
by dariomt＠gmail.com 06 Jun '19

06 Jun '19

> > >Are there instructions for developers that I've missed? > > There are some instructions here: > > > https://www.boost.org/doc/libs/1_70_0/libs/config/doc/html/boost_config/gui… > > Thanks! I was expecting developer guidelines in the github readme, not in the actual library docs! doh! I have made a PR #285 and after some trial and error (I only have VS2015 and VS2017 available to test locally) I think I have something. However, in my test I throw and catch exceptions: int test() { std::exception_ptr ep; try { throw 42; } catch(...) { ep = std::current_exception(); } try { std::rethrow_exception(ep); } catch(int i) { // return zero on success return i == 42 ? 0 : 1; } return 1; } But the CI jobs have gcc and clang configured to compile without exception support! And I get errors like: libs/config/test/boost_no_cxx11_hdr_exception.ipp:22:5: error: cannot use 'throw' with exceptions disabled throw 42; ^ libs/config/test/boost_no_cxx11_hdr_exception.ipp:20:3: error: cannot use 'try' with exceptions disabled try ^ I have two questions: 1) Where are exceptions disabled in the CI jobs? I can't find it in the .travis.yml, but I can see e.g. clang being invoked with -fno-exceptions 2) How can I test proper support for std::current_exception() and std::rethrow_exception() if exceptions are disabled for the test? Thanks!

2 1

[ boost.out_ptr ] [ Review Endorsement ] New Library targeting C++11
by JeanHeyd Meneide 04 Jun '19

04 Jun '19

Dear Boost Community, After a lot of work and discussion in-person, via e-mail, and on the Slack, I would like to ask for the library boost.out_ptr <https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr.adoc> -- targeting C++11 -- to be endorsed for review. Documentation: ascii doc-ready and readable on GitHub <https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr.adoc> Repository: GitHub <https://github.com/ThePhD/out_ptr> Standards Proposal: p1132 <https://thephd.github.io/vendor/future_cxx/papers/d1132.html> (accepted for and targeting C++20) boost.out_ptr is a library for making it easy to interoperate between smart pointers and traditional C-style initialization and allocation interfaces. It also enables doing so in a way that allows library authors to opt-into speed optimizations for their smart pointers that give them performance equivalent to typical C pointers (see benchmarks <https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr/benchmarks.adoc> and the Standard C++ proposal <https://thephd.github.io/vendor/future_cxx/papers/d1132.html#perf> for more details). Many thanks to the in-person discussion during Library in a Week at C++Now, which helped shape the implementation and yield the final Rationale <https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr/rationale.adoc>. Many thanks to Ezra (eracpp) for a lot of the quick, easy-to-read examples that became part of the documentation. Sincerely, JeanHeyd Meneide

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Re: [boost] [Boost.Config] Detect compiler support for std::current_exception
by dariomt＠gmail.com 03 Jun '19

03 Jun '19

> > >>> Hi all, > >>> > >>> I'm working on a Boost.Exception issue [1] and I need to detect > compiler > >>> support of std::current_exception. In the issue there is a suggestion > to > >>> use #if __cplusplus > 199711L but that does not work for my use case > >>> (VS2015 reports __cplusplus = 199711L). > >> > >> MSVC defines _MSVC_LANG for this[1]. At least, it used to. However, it > >> would be cleaner to have a dedicated macro in Boost.Config for this. > >> > > Totally agree. > > > >> > >>> Is it possible to add a config macro for this? > >>> Or is there a good enough existing macro I can use? > >> > >> I don't think there is. Something like BOOST_NO_CXX11_HDR_EXCEPTION > >> would be useful. > > > > I would need to detect support for std::current_exception, not the > presence > > of header <exception>, so I would think that > > BOOST_NO_CXX11_CURRENT_EXCEPTION is what I need, right? > > BOOST_NO_CXX11_HDR_EXCEPTION, as all BOOST_NO_CXX11_HDR_* macros, detect > that the header not only exists, but is usable and contains all major > components described by the standard. In case of > BOOST_NO_CXX11_HDR_EXCEPTION, that would mean std::exception_ptr, > std::current_exception, std::rethrow_exception, std::make_exception_ptr, > etc. You need at least std::exception_ptr and std::current_exception. > Thanks, that makes sense! > > Should I open an issue in github for Boost.Config? > > Yes, or better yet - make a PR. > Added github Issue #284 [1], I'll try to come up with a PR. Wondering how deep the rabbit hole goes... ^_^ Regards [1] https://github.com/boostorg/config/issues/284

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Downloads of boost from Bintray.com are temporarily unavailable
by Marshall Clow 30 May '19

30 May '19

Apparently, Boost is being downloaded over 6000 times/day from Bintray, and we've reached the limits of their bandwidth for the month. We're trying to get them to increase our quota (and see if there's someone who is downloading boost over and over again), but at the present time, downloads from bintray are being rejected. Hopefully this will be a temporary situation. -- Marshall (boost release manager)

3 2

disjoint_sets and graph appear to be Link previously defined to another file,
by Paul A. Bristow 30 May '19

30 May '19

I have just done a full GIT update from Boost develop. (and bootstrap to rebuild b2.exe) When I try to recreate the headers or run any b2 run, I now get Performing configuration checks - default address-model : 32-bit - default architecture : x86 - symlinks supported : yes error: Cannot create link ..\..\..\boost\pending\detail\disjoint_sets.hpp to ..\..\graph\include\boost\pending\detail\disjoint_sets.hpp. error: Link previously defined to another file, ..\..\disjoint_sets\include\boost\pending\detail\disjoint_sets.hpp. I deleted all the bin.v2/libs files but this has no effect. I have deleted /disjoint_sets to get going again (as I not using either graph or disjoint_sets). What am I doing wrong? Paul --- Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 (0) 1539 561830

2 1

Follow the work on Google summer of code
by David Bellot 30 May '19

30 May '19

Hi Boost community, you can follow the work of our students on this github page https://github.com/BoostGSoC19 They are all working very hard already. Best regards, David

1 0

Re: [boost] Aggregate usage statistics request for Boost
by Dimitri John Ledkov 29 May '19

29 May '19

On Fri, 3 May 2019 at 10:03, Joshua Marshall <jrmarsha(a)mtu.edu> wrote: > > Hello all, > > A few of us with Boost are trying to decide support of different compilers. I know that Ubuntu collects some anonymized statistics which could help us some. Could someone please collect and forward the following bits of information to boost(a)lists.boost.org : > Install base size of Ubuntu 14.04 to 19.04 > Per OS version, what versions of GCC, Clang, and Boost are installed on what percentage of the install base. > -- > ubuntu-devel mailing list > ubuntu-devel(a)lists.ubuntu.com > Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel >From Ubuntu development point of view, our biggest concern is that no stable releases of boost claim to be supported or tested with the next GCC compiler. For example, for 19.10 we will be switching to GCC-9 by default, yet boost 1.70.0 primary test compilers do not include GCC-9 for Linux. Ideally, we would like to see boost upstream include next-gcc as part of primary or additional test compilers for every boost release. W.R.T. Install base size ratios and which boosts are in use -> we do not have statistics on what you are asking for. I.e. default compilers are installed on all systems (to support dkms), some boost runtime libraries are also always installed as quite a few packages depend on boost runtimes. And dev packages are not tracked and impossible to tell if they are installed by accident or on purpose. We can say generically, that our LTS releases are used a lot more than non-LTS releases, and thus by extension default compilers and boost versions within those are used more. And LTS cycles do follow an overlap, where for a while after one LTS release, the previous LTS is the most popular, and then it rolls over eventually. Our default compiler is GCC for all packages. LLVM toolchain is used for mesa and intel graphics compiler, and like that's it. Mesa requirements are what drives LLVM toolchain updates in Ubuntu. Next LTS 20.04 -> to be determined Current Development 19.10 -> 1.67.0, gcc 8.3 being switched to gcc 9, clang 8.0 (or newer) Current LTS releases (most popular at the moment) 18.04 -> 1.65.1, gcc 7.4, clang 6.0 16.04 -> 1.58.0, gcc 5.3, clang 3.8 Past basic support, in Extended Maintainance Support LTS (very old, and declining in usage) 14.04 -> 1.54.0, gcc 4.8, clang 3.4 12.04 -> 1.48.0, gcc 4.6, clang 3.0 -- Regards, Dimitri.

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Re: [boost] [Boost.Config] Detect compiler support for std::current_exception
by dariomt＠gmail.com 29 May '19

29 May '19

> > > > Hi all, > > > > I'm working on a Boost.Exception issue [1] and I need to detect compiler > > support of std::current_exception. In the issue there is a suggestion to > > use #if __cplusplus > 199711L but that does not work for my use case > > (VS2015 reports __cplusplus = 199711L). > > MSVC defines _MSVC_LANG for this[1]. At least, it used to. However, it > would be cleaner to have a dedicated macro in Boost.Config for this. > Totally agree. > > > Is it possible to add a config macro for this? > > Or is there a good enough existing macro I can use? > > I don't think there is. Something like BOOST_NO_CXX11_HDR_EXCEPTION > would be useful. > I would need to detect support for std::current_exception, not the presence of header <exception>, so I would think that BOOST_NO_CXX11_CURRENT_EXCEPTION is what I need, right? So that I can #ifndef BOOST_NO_CXX11_CURRENT_EXCEPTION // I can use std::current_exception() unconditionally here #endif Should I open an issue in github for Boost.Config?

3 2

[Boost.Config] Detect compiler support for std::current_exception
by dariomt＠gmail.com 27 May '19

27 May '19

Hi all, I'm working on a Boost.Exception issue [1] and I need to detect compiler support of std::current_exception. In the issue there is a suggestion to use #if __cplusplus > 199711L but that does not work for my use case (VS2015 reports __cplusplus = 199711L). Is it possible to add a config macro for this? Or is there a good enough existing macro I can use? Thanks in advance [1] https://github.com/boostorg/exception/issues/10

2 1

My messages do not reach boost-request@lists.boost.org
by dariomt＠gmail.com 27 May '19

27 May '19

Hi, I've tried a couple of times to write to the Boost Developers mail list, but I don't see my messages getting through to the list. I seem to reach the Boost Users mil list without problems. Could you please review why this is happening? Thanks in advance!

1 0

Re: [boost] bcp namespace aliasing broken, impacts package providers, shared libraries unusable since 1.69
by Peter Dimov 26 May '19

26 May '19

> Actually, bcp already has a list of things it can't figure out > automatically: > > https://github.com/boostorg/bcp/blob/develop/add_path.cpp#L195 > > which would need to be updated... ... with something like https://github.com/boostorg/bcp/commit/365e5e74f1708425ae542698730076e52acb… Unfortunately, after these fixes, everything seems to be copied correctly, but b2.exe then crashes. Something to do with `test` using `predef`, I assume, because if I delete libs/test, it then works.

1 0

Re: [boost] bcp namespace aliasing broken, impacts package providers, shared libraries unusable since 1.69
by Peter Dimov 26 May '19

26 May '19

> It could probably be changed to copy libs/$LIB/config as a special case. Actually, bcp already has a list of things it can't figure out automatically: https://github.com/boostorg/bcp/blob/develop/add_path.cpp#L195 which would need to be updated with, I assume, std::pair<fs::path, fs::path>("libs/log/build", "libs/log/config"), and std::pair<fs::path, fs::path>("libs/test/build", "libs/predef/check"), or something like that.

1 0

Re: [boost] bcp namespace aliasing broken, impacts package providers, shared libraries unusable since 1.69
by Peter Dimov 26 May '19

26 May '19

> But as a first step I think that we need to add a Travis test to tools/bcp > that exercises the scenario we want to fix. I've looked into this and we have some issues we probably need to address even before getting to namespace aliasing. 1. Since tools/boost_install and libs/headers are now needed by Jamroot, it might be better if we install them by default when `build` is requested. (libs/config is also needed by Jamroot, but almost every other library needs it as a dependency, so this usually doesn't manifest as a problem in practice.) 2. When I add them by hand, bcp installs more than needed, because tools/boost_install/test references a number of libraries such as container, log, python, and so on; we don't need these for typical uses. 3. Installing these libraries exposed issues with them: 3a. Log doesn't work because it has jamfiles in libs/log/config, which is not copied (just `build` and `src` are.) 3b. Test doesn't work because it uses predef.check in its Jamfile, but Predef is not copied. Apart from that, https://travis-ci.org/boostorg/bcp/builds/537447552

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Re: [boost] bcp namespace aliasing broken, impacts package providers, shared libraries unusable since 1.69
by Peter Dimov 26 May '19

26 May '19

> Apart from that, https://travis-ci.org/boostorg/bcp/builds/537447552 After fixing the two problems in Jamroot, testing the library after --namespace still doesn't work, because libs/program_options/test/Jamfile.v2 refers to the library as boost_program_options, but it's no longer called that.

1 0

[iostreams] Interest in multithreaded lzma filter?
by Mike 26 May '19

26 May '19

Accidentally only sent this to James and not the ML: > Gesendet: Donnerstag, 23. Mai 2019 um 15:19 Uhr > Von: "James E. King III" <jking(a)apache.org> > > > On Thu, May 23, 2019 at 8:39 AM Mike via Boost <boost(a)lists.boost.org> wrote: > > > > > Gesendet: Mittwoch, 22. Mai 2019 um 23:40 Uhr > > > Von: "Jeff Bonyun via Boost" <boost(a)lists.boost.org> > > > > > > > ... How will we detect whether > > > > liblzma is capable? If it is not capable but specified, will we allow > > > > the compression anyway? > > > > > > I've been investigating this. liblzma defines a version macro, > > > LZMA_VERSION. It looks like liblzma obtained its multithreaded function > > > in 5.1.1 (in 2011). So the idea would be to branch on this macro, and > > > fall back to the currently-used single-threaded function for an older > > > liblzma version. In that case, requesting any number of threads will > > > carry out the operation, but will only use a single thread. This makes > > > it tolerant of different versions, but does mark up the code with a few > > > #if branches. I'm assuming boost goes for tolerance in this case. > > > > Does a 2019 Boost release really have to be compatible with a Pre 2011 > > release of liblzma? Is this combination even tested? > > I.e. are we sure this would be the only incompatibility? > > > > How about just adding this functionality unconditionally and see if > > someone complains? > > > > So basically if someone has an older lzma they are limited to boost > 1.70.0 or earlier. That's perhaps reasonable as long as it is > documented, but it hasn't been the typical way I have seen things > added to existing code. Well, my second question was if you are confident that 1.70 does actually work with liblzma versions older than 5.1.1? If this isn't tested, it is not supported and if it is not supported it imho makes little sense to complicate the source code to achieve potential compatibility with (what I assume to be) a very, very small number of setups. > > Another way to handle it is to keep the old path in a macro like > BOOST_IOSTREAMS_NO_MULTITHREADED_LZMA. This is common through boost. > Ideally, detecting the liblzma version from the header could then set > BOOST_IOSTREAMS_NO_MULTITHREADED_LZMA and it would always do the right > thing, but the simplest way to do it is to let the consumer of the > library set this if they need it. > Personally I'm not a fan of configuration macros when they are not absolutely necessary because it effectively means you introduce yet another variant of boost that may or may not be tested and may or may not be compatible with the variant another dependency in my project was tested with (The total configuration space of boost is already far too large for my taste). As Robert Schumacher said in his cppcon talk: It's not just about you and the user, but also every library between you and the user. All of them now either have to support both choices or have to make one choice and hope they don't become incompatible with a different 3rd party library. Yet another reason, why package & dependency management is so hard in c++. However, as long as the interface is untouched by this macro I guess it would be fine. Best Mike

3 3

Non-ASCII Path Names in Repo
by Tom Kent 25 May '19

25 May '19

In the last few days we've had a non-ASCII path name added to the repo: tools/boostdep/test/utf8-test-ßµ™∃ Which came with commit 8893d1c57951a [1] I noticed this because a python 2 script (calling shutil.copytree) I had running on windows that copied the repo around started to fail. I've long needed to update that script to python 3, and am working on this. However, I wanted to point this out to the list so we could discuss if there are any other ramifications of having a non-ascii path. I vaguely remember some discussion about something like this in the past, but couldn't find it via search. If this is already a settled topic, that's great. Tom [1] https://github.com/boostorg/boostdep/commit/8893d1c57951a4a83705ed203005576…

2 1

bcp namespace aliasing broken, impacts package providers, shared libraries unusable since 1.69
by Mathias Gaunard 25 May '19

25 May '19

Hi, I'd like to point out that bcp namespace aliasing has been broken for quite a while, which impacts package providers of Boost which choose to package it with a versioned namespace. We should try to fix to enable more people to upgrade. The bug has been reported March 2018 on trac https://svn.boost.org/trac10/ticket/13460 Then again by me this week on github https://github.com/boostorg/bcp/issues/4 Things have been made worse since 1.69 because libraries now build with visibility hidden by default, which means that with this bug symbols don't get exported and nothing links. Also I would argue that this set-up should be tested as part of the release validation process. The boost build system is arcane enough that we don't need a pretty standard build configuration to be subtly broken for more than a year. Could we try to address this before 1.71?

3 3

[iostreams] Interest in multithreaded lzma filter?
by Jeff Bonyun 23 May '19

23 May '19

I've implemented a multithreaded update to iostreams' lzma filter for my own purposes, and I was wondering if this change would be considered for including in Boost.iostreams? It uses liblzma's own multithreaded functions, so the changes to boost are actually pretty minimal. It does add a new member to the boost-provided lzma options struct -- to specify your desired number of threads -- which changes how people might use the constructor for the filter. My two biggest concerns with including it in Boost.iostreams are: - Making the filter constructor backwards compatible. Right now, users can initialize the options struct with a single unbraced int when calling the filter constructor. With the change to the struct, I want to make sure this old way still works. I.e. not requiring a braced initializer list if you only want to provide the compression level. - Handling older versions of liblzma that didn't offer multithreading. I'll work on identifying the exact versions needed, and branching on their #defined version numbers. If there is appetite for it, I can make a pull request on github. As this would be my first submission to boost, I'm sure I'll screw something up and need correcting, so be patient. Jeff

3 5

Using 'vcunk' toolset.
by Olaf van der Spek 22 May '19

22 May '19

Hi, Any chance to support 16.2 (preview 1)? ********************************************************************** ** Visual Studio 2019 Developer Command Prompt v16.2.0-pre.1.0 ** Copyright (c) 2019 Microsoft Corporation ********************************************************************** C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview>cd \vc C:\VC>cd boost_1_70_0 C:\VC\boost_1_70_0>./boost '.' is not recognized as an internal or external command, operable program or batch file. C:\VC\boost_1_70_0>./bootstrap.bat '.' is not recognized as an internal or external command, operable program or batch file. C:\VC\boost_1_70_0>bootstrap.bat Building Boost.Build engine Failed to build Boost.Build engine. Please consult bootstrap.log for further diagnostics. bootstrap.log: Found with vswhere Visual Studio Locator version 2.6.7+91f4c1d09e [query version 2.1.1046.44959] Found with vswhere Visual Studio Locator version 2.6.7+91f4c1d09e [query version 2.1.1046.44959] ### ### Using 'vcunk' toolset. ### C:\VC\boost_1_70_0\tools\build\src\engine>if exist bootstrap rd /S /Q bootstrap C:\VC\boost_1_70_0\tools\build\src\engine>md bootstrap C:\VC\boost_1_70_0\tools\build\src\engine>cl /nologo /RTC1 /Zi /MTd /Fobootstrap/ /Fdbootstrap/ -DNT -DYYDEBUG -wd4996 kernel32.lib advapi32.lib user32.lib /Febootstrap\jam0 command.c compile.c constants.c debug.c execcmd.c execnt.c filent.c frames.c function.c glob.c hash.c hdrmacro.c headers.c jam.c jambase.c jamgram.c lists.c make.c make1.c object.c option.c output.c parse.c pathnt.c pathsys.c regexp.c rules.c scan.c search.c subst.c timestamp.c variable.c modules.c strings.c filesys.c builtins.c md5.c class.c cwd.c w32_getreg.c native.c modules/set.c modules/path.c modules/regex.c modules/property-set.c modules/sequence.c modules/order.c command.c compile.c constants.c debug.c execcmd.c execnt.c filent.c frames.c function.c glob.c hash.c hdrmacro.c headers.c jam.c jambase.c jamgram.c lists.c make.c make1.c object.c Generating Code... Compiling... option.c output.c parse.c pathnt.c pathsys.c regexp.c rules.c scan.c search.c subst.c timestamp.c variable.c modules.c strings.c filesys.c builtins.c md5.c class.c cwd.c w32_getreg.c Generating Code... Compiling... native.c set.c path.c regex.c property-set.c sequence.c order.c Generating Code... C:\VC\boost_1_70_0\tools\build\src\engine>.\bootstrap\jam0 -f build.jam --toolset=vcunk "--toolset-root=Visual Studio Locator version 2.6.7+91f4c1d09e [query version 2.1.1046.44959]\Common7\Tools\..\..\VC\ " clean ### ### Unknown toolset: vcunk ### ### Known toolsets are: acc, borland, cc, como, clang, darwin, gcc, gcc-nocygwin, intel-darwin, intel-linux, intel-win32, kcc, kylix, metrowerks, mipspro, msvc, qcc, pathscale, pgi, sun, sunpro, tru64cxx, vacpp, xlcpp, vc7, vc8, vc9, vc10, vc11, vc12, vc14, vc141, vc142, vmsdecc ### C:\VC\boost_1_70_0\tools\build\src\engine>.\bootstrap\jam0 -f build.jam --toolset=vcunk "--toolset-root=Visual Studio Locator version 2.6.7+91f4c1d09e [query version 2.1.1046.44959]\Common7\Tools\..\..\VC\ " ### ### Unknown toolset: vcunk ### ### Known toolsets are: acc, borland, cc, como, clang, darwin, gcc, gcc-nocygwin, intel-darwin, intel-linux, intel-win32, kcc, kylix, metrowerks, mipspro, msvc, qcc, pathscale, pgi, sun, sunpro, tru64cxx, vacpp, xlcpp, vc7, vc8, vc9, vc10, vc11, vc12, vc14, vc141, vc142, vmsdecc ### C:\VC\boost_1_70_0\tools\build\src\engine>exit /b 1 -- Olaf

1 0

[config] Disabling symbol visibility?
by John Maddock 19 May '19

19 May '19

We have an open ticket from someone that wants all symbols hidden, including those marked with BOOST_SYMBOL_VISIBLE, is this sensible to support? What are the likely consequences of doing so? See https://github.com/boostorg/config/issues/243 Thanks in advance, John. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

3 2

[gsoc19] Introduction
by Thomas Ferrand 18 May '19

18 May '19

Hello everyone, I am Thomas Ferrand a french student in computer science and I am happy to take part in GSoC this summer. I will be working on Boost.SafeFloat (https://github.com/sdavtaker/safefloat) a library that aims at helping developers detecting errors in floating point numbers computations. Best regards, Thomas Ferrand

3 2

[GSoC19] Greetings
by Kim 18 May '19

18 May '19

Hello, Another student and I will be contributing to the proposed Boost library, Real, with mentors Damian Vicino and Laouen Belloli. My name is Kimberly Swanson. I am a mathematics undergrad at University of Central Florida. My primary focus during the summer will be to improve the memory complexity of Real's internal representation. After the main changes, I plan to implement benchmarks with Google Benchmark (though I am open to using other libraries, if recommended). Future changes made regarding memory/computational complexity would refer to results from the benchmark. I aim to get it to a review-ready state before the end of GSoC (fingers crossed). Warm Regards, Kim

2 1

[variant2] Acceptance conditions met - Targeted for 1.71.0
by Michael Caisse 17 May '19

17 May '19

Peter Dimov has updated the Variant2 library based on review acceptance criteria. I have reviewed the changes and "OK" Variant2 to be included as a Boost library. My understanding is that Peter is targeting Variant2 to be available in the 1.71.0 release. Congratulations Peter! Thank you for your quick work in updating the library based on the review feedback. -- Michael Caisse Ciere Consulting ciere.com

2 1

Need help setting up Travis CI and codecov
by Sagnik Dey 15 May '19

15 May '19

We are getting ready to start work on the Boost.Real project and getting Travis CI and codecov integration for the new repository https://github.com/BoostGSoC19/Real, would be a great help. Can someone please provide some help as to how to set it up? The yml files for both travis and codecov are already present in the repo as this is a fork from an older repo that had a working travis and codecov integration. Thank You, Sagnik Dey

2 1

[GSOC19] Introduction
by Ashar 15 May '19

15 May '19

Hi, My name is Mohammad Ashar Khan, I will be working on uBLAS to bring better expression templates support using boost.YAP. I will also be adding support for expression optimization using mathematical laws. Regards Mohammad Ashar Khan

1 0

[Real] [GSoC19] Working together on Real
by Kim 15 May '19

15 May '19

Hello, Sagnik Dey and I, both GSoC19 students, will work together on Real. Laouen Belloli suggested we reach out to the dev list regarding how we will work with the BoostGSoC19/Real repo. Should we 1. work on the same repo using different branches, or 2. each make a fork of the repo We have some overlapping tasks from our GSoC proposals, and plan on possibly implementing different implementations for some thing(s), while dividing up the tasks between ourselves for others. Further, we would like to get Travis CI and codecov in the respective repo(s), but we need to know which option we're going with first. Best Regards, Kim

1 0

[GSOC19] Introduction
by Amit Singh 15 May '19

15 May '19

Hello everyone, My name is Amit Singh. I will be contributing to ublas tensor this summer. My goal is to improve the design and integrating new features to tensor. Best Regards Amit Singh

1 0

Re: [boost] [ Interest? ] [ out_ptr ] Tiny C++ Abstraction for C-Style Output Pointers
by Bjorn Reese 12 May '19

12 May '19

On 06/28/18 21:03, ThePhD via Boost wrote: > out_ptr is a small abstraction for making types such as > std::unique_ptr, std::shared_ptr, boost::shared_ptr, and the upcoming > std::retain_ptr > <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0468r0.html> work > work C-Style output functions as a parameter, addressing the need of > wanting to be able to do "my_c_api_init( foo, bar, &my_smart_ptr );". It's Does out_ptr have other use-cases than C interoperability?

7 14

[variant2] Review Results
by Michael Caisse 11 May '19

11 May '19

First, I would like to apologize to Peter and the those who took time to review Boost.Variant2 for the slow turn-around of a result. Thank you Peter for producing and submitting such a high-quality library for review. The code has been a pleasure to read and review. Thank you to the reviewers! Your participation in the process is what makes Boost libraries high-quality. I personally appreciate the time and effort that each of you have put into this review. ------------- Result ------------- Boost.Variant2 will be ACCEPTED after the following changes are made. An additional review will not be required. - The library will implement the strong guarantee: - If all alternatives have nothrow move, single buffer - else, double buffer - Improved documentation: - Addition of a tutorial - Addition of design motivation - Peter has indicated that triviality propagation will come in a future version. The initial Boost release need not support triviality propagation. - Expected will not be included but may be submitted for review at another time. ---------------- Review Verdicts ---------------- The following people provided reviews. Reject ---------- Andrezj Krzemienski Antony Polukhin Jan Herrmann Accept ---------- Emil Dotchevski Gavin Lambert Phil Endecott Conditionally Accept -------- Bjorn Reese Andrey Semashev Damian Jarek Niall Douglas Andrezj and Antony’s rejections were based on not having a valueless-by-exception state. Neither saw the selected design space worth considering and each believed the trade-off was dangerous for users. The Conditional Acceptance reviews voiced the following: - Strong preference for the strong guarantee (and therefore no need to provide “surprising” behaviour for the state after an exception.) - Improved documentation containing both tutorial and motivation sections. - Triviality propagation of the variant types. - Accepted without expected being contained. -------------- Some Thoughts -------------- There was a good amount of healthy discussion on the Developer Mail List concerning Variant2. I want to thank all of the participants for engaging with civility and keeping to the technical merits despite the galvanized opinions concerning valueless-by-exception and the basic exception guarantee. Over the past couple weeks I have re-read all of the discussion threads 3 or 4 times. While some people didn’t find value in the exchanges, this level of engagement about design trade-offs is one of the attributes that sets Boost reviews apart. They are not merely reviews discussing the quality of implementation but also the intricacies of design choices within the constraints and consistency of the language. When reviewers articulate their opinions the entire community learns and grows. The trade-offs that Peter made seem dangerous to some yet the exact correct formulation for others. There are even standard library implementers that don’t agree with std::variant’s valueless-by-exception. A high-quality variant that provides the strong exception guarantee is a type that has been missing from the programmer toolbox. Variant2 provides this. I will make an additional announcement to the community when the conditions for acceptance have been met. Thank you all for making Boost better! michael -- Michael Caisse Ciere Consulting ciere.com

7 6

To modularize, or not to modularize. What is the plan?
by Rene Rivera 10 May '19

10 May '19

Bringing this up because of the recent discussion in the 1.70.1 thread. And of course because this is the week that a certain BSC meets. Hence I thought I would clarify what I've meant my a modular Boost all this time. A modular Boost, to me, means a Boost that first and foremost a collection of independently consumable C++ libraries. That would have the following aspects to it: * An end user or library author can obtain a single Boost library of their choice and use it in their project, assuming they also obtain the appropriate dependencies of that library. * BoostOrg would not produce a monolithic, combined, merged, etc distribution. * BoostOrg would produce collectively tested milestone modular distributions. Sounds lovely right? ...I'll leave the discussion of merits to responses herein ;-) What would it take to reach that modular goal? Why do I keep saying we've been working on this for ages and ages? Briefly here's what it would take to get there (not in any particular order): * Abandon the single header include tree. * Abandon the monolithic build infrastructure. * Ban relative use of inter-library dependencies. * Explicit declaration of inter-library dependencies. * Strict normalized library layout. * Remove, and ban, dependency cycles at the inter-library user consumable granularity. There's probably more items that I've forgotten above. But this should be enough to converse about. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net

14 63

[boost-ci][azp] Configuration for Azure Pipelines
by Mateusz Loskot 09 May '19

09 May '19

Hi, FYI, James approved and merge my submission of Azure Pipelines to the repository with common CI configuration templates. Here is the PR: https://github.com/boostorg/boost-ci/pull/16 The AzP configuration follows common conventions from the existing templates for Travis CI and AppVeyor, and steals from Boost.Build's azure-pipelines.yml crafted by Rene with a few pinches of AzP experience from Boost.GIL. The boost-ci README.md provides more details. Although James maintains boost-ci, he is neither able to test the AzP configuration (I tested it quite extensively myself) nor maintain it. If you will give it a go and notice any problems, please open new issues for boost-ci and I will do my best to help. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Fingerprint=C081 EA1B 4AFB 7C19 38BA 9C88 928D 7C2A BB2A C1F2

1 0

Introducing me, Sagnik Dey
by Sagnik Dey 08 May '19

08 May '19

Hello! I am pleased to announce that I will be working on the Boost.Real project as part of GSoC'19. Looking forward to a productive summer, producing quality code and getting to know the developer community better. Thank You, Sagnik Dey

1 0

Re: [boost] [doc][signals] Broken links for Boost 1.70
by Glen Fernandes 08 May '19

08 May '19

On 2019-04-15 at 21:46:18 Mateusz Loskot wrote: > On https://www.boost.org/doc/libs/1_70_0/ links to these documentations are broken: > > https://www.boost.org/doc/libs/1_70_0/libs/signals/ > > Could anyone help to identify what is going wrong with those and how to fix it? Signals was removed as a Boost library starting with in 1.69.0 and I had put a notice in the 1.69 release notes about this (section "Discontinued Libraries"). I've removed the links for Signals (v1) on the Libraries page going forward. e.g. https://www.boost.org/doc/libs/develop/libs/libraries.htm e.g. https://www.boost.org/doc/libs/develop/ Additionally, I've added an entry in the "Libraries Retired from Boost" on that first libraries page for Signals (v1) alongside compose. Glen

2 1

[any] ABI break
by Antony Polukhin 07 May '19

07 May '19

Hi, I'm planning to apply an ABI breaking change to the Boost.Any https://github.com/boostorg/any/pull/11 That PR makes the binaries that use boost::any smaller. For example libboost_program_options.so looses 4KB in size. Boost libraries were not guaranteeing ABI stability, but boost::any is quite often used across library boundaries. Double checking that there's no objections.

1 1

Lets do 1.70.1 WHO IS WITH ME!!!
by Vinnie Falco 06 May '19

06 May '19

A crashing defect in Beast was discovered shortly after release: <https://github.com/boostorg/beast/issues/1599> It happens under high load when things happen at just the right time (or wrong time depending on how you look at it). It *will* eventually happen to any long-lived connection that sees enough traffic and timeouts. The fix is trivial: <https://github.com/vinniefalco/beast/commit/8620439f8e38db62713cff55a428bf8…> Thanks to the detailed report we were able to write a unit test which reproduces it reliably. Is this worth putting up a 1.70.1 for? The timeout feature is new in 1.70 and it is rather a shame that people might not be able to use it because of a defect. Regards

8 19

b2 --layout=versioned compiler tag in library filename
by Paul Harris 06 May '19

06 May '19

Hi guys, In the past, b2 would build libraries named like so: libboost_atomic-gcc48-mt-d-1_60.so (note -gcc48-) I tried compiling Boost 1.66.0 (from boost-git) with gcc 8.3.0, but the library it generates is named: libboost_atomic-gcc-mt-d-x64-1_66.so (note the -gcc-) No compiler version number in the tag... I (and CMake) was expecting it to be named: libboost_atomic-gcc83-mt-d-x64-1_66.so (note the -gcc83-) To build, I did: ./bootstrap.sh --with-libraries="atomic" ./b2 --layout=versioned I then downloaded the 1.70.0 tarball and compiled that, and this time the result was: tar xfv boost_1_70_0.tar.bz2 cd boost_1_70_0/ ./bootstrap.sh --with-libraries="atomic" ./b2 --layout=versioned ls -l stage/lib libboost_atomic-gcc8-mt-d-x64-1_70.so I don't see any documentation around the compiler version tag, what is the current policy? thanks, Paul

5 7

[thread] compiler error gcc 7.3 on cygwin
by James E. King III 06 May '19

06 May '19

Getting an internal compiler error with gcc 7.3 but only on cygwin 64-bit. Jim@pulsar /cygdrive/c/boost/libs/thread $ ../../b2 --abbreviate-paths toolset=gcc cxxstd=11 define=_POSIX_C_SOURCE=200112L define=__USE_ISOC99 threadapi=pthread address-model=64 variant=release -q ... gcc.compile.c++ ../../bin.v2/libs/thread/test/test_10963_c.test/gcc-7.3.0/rls/cxstd-11-iso/thrd-mlt/vsblt-hdn/test_10963_c.o In file included from ../../boost/thread/detail/invoker.hpp:30:0, from ../../boost/thread/future.hpp:31, from ../../libs/thread/test/test_10963.cpp:13: ../../boost/thread/detail/invoke.hpp: In function ‘decltype (*(forward<A0>)(boost::detail::invoke::a0).*boost::detail::invoke::f) boost::detail::invoke(Fp&&, A0&&) [with Fp = void (boost::executors::basic_thread_pool::*)(); A0 = boost::executors::basic_thread_pool*]’: ../../boost/thread/detail/invoke.hpp:102:43: internal compiler error: in gimplify_expr, at gimplify.c:12006 return (*boost::forward<A0>(a0)).*f; ^ Please submit a full bug report, with preprocessed source if appropriate. See <https://gcc.gnu.org/bugs/> for instructions. "g++" -std=c++11 -fvisibility-inlines-hidden -m64 -mthreads -O3 -finline-functions -Wno-inline -Wall -pedantic -fvisibility=hidden -Wextra -Wno-long-long -Wno-unused-parameter -Wunused-function -pedantic -DBOOST_ALL_NO_LIB=1 -DBOOST_THREAD_THROW_IF_PRECONDITION_NOT_SATISFIED -DNDEBUG -D_POSIX_C_SOURCE=200112L -D__USE_ISOC99 -I"../.." -c -o "../../bin.v2/libs/thread/test/test_10963_c.test/gcc-7.3.0/rls/cxstd-11-iso/thrd-mlt/vsblt-hdn/test_10963_c.o" "../../libs/thread/test/test_10963.cpp" ...failed gcc.compile.c++ ../../bin.v2/libs/thread/test/test_10963_c.test/gcc-7.3.0/rls/cxstd-11-iso/thrd-mlt/vsblt-hdn/test_10963_c.o... If I change the C++ language level to 03 the problem goes away. I also cannot reproduce it on linux with the same version of compiler (but it probably isn't the exact same compiler code). Should I go ahead and file that gcc bug? - Jim

2 1

[boost-ci] Extended list of branches allowed to build
by Mateusz Loskot 03 May '19

03 May '19

Hi, This is to inform maintainers and contributors about little proposal I made to the common CI infrastructure maintained by James https://github.com/boostorg/boost-ci/pull/11 The comments should explain rationale behind extending the common naming convention to enable CI builds for topic branches (w/o changing branch filters in .travis.yml etc.). The PR has now been merged. I'd like to encourage mainainers who use the boost-ci setup to pull the update into the libraries. It may also be helpful to put a note in CONTRIBUTING.md or README.md to let contributors know that if they wish to test their contributions on their own CI accounts prior submitting it as PR, they should name their topic branches with prefixes: feature/*, fix/* or pr/* I hope this simple change to boost-ci would be adopted by across Boost libraries and make some contributors' life esier. "What would be great for one off contributors like me is if all CI scripts would support testing of feature branches in forked repositories by default." - from #boost at cpplang.slack.com Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Fingerprint=C081 EA1B 4AFB 7C19 38BA 9C88 928D 7C2A BB2A C1F2

1 0

[graph] Plans to upgrade algorithms with Boost.Parameter named arguments
by Cromwell Enage 03 May '19

03 May '19

Hello, everyone! With the most significant changes to Boost.Parameter now in both the 'master' and 'develop' branches, one of my next major goals is to prepare a pull request to incorporate Boost.Parameter named arguments into Boost.Graph algorithms that currently use bgl_named_params. My personal fork, <https://github.com/CromwellEnage/graph>, has a working version of such algorithms. However, I'd like your feedback on how to upgrade the corresponding documentation. I have a rough draft for documenting the Boost.Parameter-enabled A* algorithms here for your review: < https://github.com/CromwellEnage/graph/blob/develop/doc/astar_search.html>. Please suggest improvements or state if you are sufficiently satisfied with its current form to be able to use the A* algorithms with Boost.Parameter named arguments. I plan to use the same documentation style for the other affected algorithms. Regards, Cromwell D. Enage

1 0

[disjoint_sets] content moved into boostorg/graph
by James E. King III 02 May '19

02 May '19

The CMT was maintaining a standalone repository for one class, disjoint_sets, of which the only internal boost usage was in graph and graph_parallel (which depends on graph). disjoint_sets has been moved into boostorg/graph on develop. The superproject has a PR to remove it as a submodule, and the boostdep tools has a PR to remove it from an exclusion list. The path to the header has been preserved, so external usage will remain unaffected for those who download boost as a package, as disjoint_sets is header-only. If you experience any issues on develop relating to the header boost/pending/disjoint_sets.hpp, make sure you have the latest boostorg/graph, and you can manually remove libs/disjoint_sets from your sandbox, that should resolve it until the other PR in the superproject comes along. Even after that is merged, I'm not sure how the defunct disjoint_sets will be handled in sandboxes and may still need to be manually removed. There is no useful content in disjoint_sets at this point. I had experienced some complaints from b2 about being unable to link the header because it was coming from the old repository when I staged this change. Thanks, Jim

2 1

[variant] Heads-up!
by Antony Polukhin 02 May '19

02 May '19

Hi, I've merged a very cool optimization by Nikita Kniazev into the master branch. From now on boost::variant does pointer stealing for recursive variants. This significantly improves the performance of the variants move constructors. However if you use a variant variable after the std::move for anything except destruction and assignment then you're getting an UB. Beware! -- Best regards, Antony Polukhin

9 25

Re: [boost] [variant] tests failing on master
by Nikita Kniazev 30 Apr '19

30 Apr '19

> boost.variant tests are failing on master. Whatever the bug is, it is also causing my signals2 tests that use variant to fail. Config needs develop to master merge to resolve the issue.

1 0

[variant] tests failing on master
by Frank Mori Hess 30 Apr '19

30 Apr '19

boost.variant tests are failing on master. Whatever the bug is, it is also causing my signals2 tests that use variant to fail. -- Frank

1 0

Re: [boost] [variant] Heads-up!
by Nikita Kniazev 29 Apr '19

29 Apr '19

There seems to be misunderstanding of what the thread is about. The short sum-up of the changes: Nothing changed for users that does not use recursive variant. The changes were applied mainly for recursive_wrapper, and affect recursive variant indirectly. The PR was proposed as a solution for two major recursive variant problems: * Move-only types support * Poor move performance (because of this one Spirit has its own variant) Most of the users are not affected by recursive_wrapper move constructor change. To hit it you have to visit (either directly, or with applying comparison operators) a recursive moved-out variant. > have to agree with Steven. Never empty guarantee is a crucial difference between Boost.Variant and std::variant. std::variant has no recursive variant support. In the common field nothing changed. See the comment above. > If the one negative is adding UB to valid existing code at the next point release, doesn't that outweigh any number of positive outcomes? I do not think there even a single user that visits moved-out variants. There is an assertation for such usage though. > Why wouldn't this be an opt-in strategy - this property of moves has been established for years now. Because it solves the bigger problems and for much more users that it potentially breaks.

2 2

[MP11] Loosing const-qualification on type result with GCC 4.8 only
by Mateusz Loskot 28 Apr '19

28 Apr '19

Hi, (initially posted to https://lists.boost.org/boost-users/2019/04/89778.php) I prepared a lenghty MWE which reproduces my problem with type manipulation using MP11 that for some reason looses const-qualification on a ::type result Here it is at https://godbolt.org/z/eCsakP and copied below. I hope the XXXXXX comments make sense and important static assertions in the main() at the bottom explain what is the expected result. ``` #include <boost/mp11.hpp> #include <cstdint> #include <type_traits> namespace mp11 = boost::mp11; template <typename BitField, int FirstBit, int NumBits, bool IsMutable> struct bit_range_reference { /* long definition, irrelevant */ }; template <typename BitField, typename FirstBit, typename NumBits> struct bit_range_reference_type { using type = bit_range_reference < BitField, FirstBit::value, NumBits::value, true > const; // XXXXXX Why this const gets lost with GCC 4.8 XXXXXX }; template <typename BitField, typename RangeBitSizes> class bit_range_reference_list { template <typename FirstBit, typename NumBits> using reference_type = typename bit_range_reference_type < BitField, FirstBit, NumBits >::type; // XXXXXX Should carry the const, shouldn't? GCC >4.8 do. // If RangeBitSizes is mp11::mp_list_c<int,7,7,2> // then first_bit_list will be mp11::mp_list_c<int,0,7,14,16> using first_bit_list = mp11::mp_fold_q < RangeBitSizes, mp11::mp_list<std::integral_constant<int, 0>>, mp11::mp_bind < mp11::mp_push_back, mp11::_1, mp11::mp_bind < mp11::mp_plus, mp11::mp_bind<mp11::mp_back, mp11::_1>, mp11::_2 > > >; static_assert(mp11::mp_at_c<first_bit_list, 0>::value == 0, "first bit must be 0"); public: using type = mp11::mp_transform < reference_type, mp11::mp_pop_back<first_bit_list>, RangeBitSizes >; }; using reference3_list = typename bit_range_reference_list < std::uint8_t, mp11::mp_list_c<int, 3> >::type; int main() { using r1_t = mp11::mp_at_c<reference3_list, 0>; using r2_t = bit_range_reference<std::uint8_t, 0, 3, true>; using r2c_t= bit_range_reference<std::uint8_t, 0, 3, true> const; //#if defined(__GNUC__) && (__GNUC__ == 4) // GCC 4.8 compiles, later versions of GCC fail to compile static_assert(std::is_same<r1_t, r2_t>::value, "GCC says r1_t is const-qualified"); //#else // GCC 4.9, 5, 6, 7, 8 versions compile, GCC 4.8 fail to compile static_assert(std::is_same<r1_t, r2c_t>::value, "GCC says r1_t is NOT const-qualified"); //#endif } ``` To summary, I expect this to yield true: std::is_same < mp11::mp_at_c<reference3_list, 0> bit_range_reference<std::uint8_t, 0, 3, true> const > I got this confirmed by all GCC versions but GCC 4.8. (clang and MSVC also seem to agree with the GCC >= 4.9) Is mp11::mp_transform loosing const-qualification or have I made a mistake somewhere? I'm using Boost.MP11 from Boost 1.70 and from current develop branch Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

2 3

[endian] Request for comments
by Peter Dimov 28 Apr '19

28 Apr '19

There are two things that I suspect need to be fixed in Boost.Endian, but the changes are breaking. 1. endian_arithmetic<...> derives publicly from endian_buffer<...>. Intuitively, this inheritance relationship doesn't seem right, and it prevents endian_arithmetic from being a C++03 POD, due to having a base class. 2. the data() member function returns char const*. This type is strongly associated with null-terminated strings, and as such, using it for the underlying bytes of the endian object seems error-prone. I'd much prefer to return `unsigned char const*` from data() (although in C++17 `std::byte const*` might be even better.) I can't however estimate with any certainty whether the (mostly aesthetic) benefit of these changes would outweigh the users' annoyance from their code being broken for no strong reason. Comments?

4 3

CMake, modular Boost, and other stories
by Mike 27 Apr '19

27 Apr '19

Coming at this from a different angle: It might make sense to reserve find_package(Boost_foo) for libraries that directly support installation from cmake. Not sure if such a split is a good idea, but I wanted to put it up for consideration. Best Mike

3 3

PartIcpation in Boost
by Edward Diener 27 Apr '19

27 Apr '19

For personal reasons I will not be able to participate in Boost as I have in the past, which means I will no longer be able to be part of CMT. I will continue to maintain the libraries I created for Boost, tti and VMD, as well as maintaining the preprocessor library created by Paul Mensonides. This means that I will not have the time or the will to be involved with other libraries any more, except on the most general level of discussion. For what it is worth I think that Cromwell Enage should become the maintainer of the Parameter library. I have not, and still do not understand, why when talented C++ programmers are willing to contribute heavily to Boost they are not encouraged and supported more. But this is not my problem. For those who are interested, the experimental C++ standard preprocessor which had been added for VC++ in VS2017 via the '/experimental:preprocessor' switch is still supported in VS2019, although not documented anywhere in the official VS2019 docs. Ths VC++ experimental preprocessor is fully supported in Boost PP and Boost VMD. Unfortunately this preprocessor can not pass all the Boost PP tests, although it has gotten a little better in VS2019 from VS2017. I posted bug reports in Microsoft's bug reporting system regarding its bugs. I have not bothered to test it with the VMD tests, since if it can not pass all the PP tests it is not going to pass the VMD tests. Also while clang on Windows, whether targeting gcc or VC++, passes all the Boost PP tests it fails to pass the VMD tests with lots of errors, seemingly because it is running out of memory ( ? ). I have not bothered reporting this to clang, since my previous experience has shown me that they are clearly not that interested in their Windows implementation. Both gcc on both Linux and Windows, and clang on Linux, pass all the Boost PP and VMD tests. Of course you can try all this out for yourself if you are interested. Edward Diener

3 2

Re: [boost] CMake, modular Boost, and other stories
by Mike 27 Apr '19

27 Apr '19

> +1. Aside from the other benefits mentioned: What benefits exactly? I don't think anyone has mentioned any benefits of dropping the second form at all at all. This isn't an "either or" question - currently both versions are supported. So why exactly should one be dropped? We have talked a lot about Modularization, but little about the original question. Best Mike

1 0

CMake, modular Boost, and other stories
by Peter Dimov 26 Apr '19

26 Apr '19

It's been quiet lately, so it must be time for another CMake discussion. As you know, Boost 1.70 installs CMake configuration files on `b2 install`, and we've started to receive feedback, some of which more interesting than what doesn't work. At present, `b2 install --with-filesystem` for example installs a configuration file boost_filesystem-config.cmake, which enables CMake users to issue the command `find_package(boost_filesystem)` and then use Boost.Filesystem. This mimics what an ordinary, independent library that happened to be called "boost_filesystem" would do. It also installs an umbrella BoostConfig.cmake file, which enables the alternative use of `find_package(Boost COMPONENTS filesystem)`, which treats Filesystem as a component of the package Boost, rather than as a standalone library. This is compatible with the existing, pre-1.70 use of FindBoost.cmake to locate Boost from CMake. Brad King (from Kitware, who should know) argues that installing separate configuration files for all the libraries is wrong. He says that the preferred practice is to only support the second use, with Boost as the package, and the libraries as components, not accessible as packages on their own. (The discussion is here: https://gitlab.kitware.com/cmake/cmake/issues/19186) The reason I went with installing separate configuration files was that I expected that (a) this would be our preferred future approach when, or if, we switch to building with CMake and (b) even if not, this seemed like a step in the right, "modular", direction where libraries are treated as independent rather than parts of the monolithic package Boost. I'm having second thoughts though. It looks to me that Brad is right, and that the various library configuration files should be implementation details of a single Boost package (in the CMake sense) and not be user-visible. That is, only support find_package(Boost COMPONENTS filesystem) and drop find_package(boost_filesystem) Thoughts?

7 11

[build] b2 help moving disjoint_sets
by James E. King III 26 Apr '19

26 Apr '19

I have merged disjoint_sets into boostorg/graph locally and submitted a pull request for it (https://github.com/boostorg/graph/pull/169) The build jobs are failing however, due to disjoint_sets already existing and already having links: https://ci.appveyor.com/project/jzmaddock/graph/builds/24131163/job/uguk1li… b2 headers Performing configuration checks - default address-model : 32-bit - default architecture : x86 - symlinks supported : yes error: Cannot create link boost\pending\detail\disjoint_sets.hpp to libs\graph\include\boost\pending\detail\disjoint_sets.hpp. error: Link previously defined to another file, libs\disjoint_sets\include\boost\pending\detail\disjoint_sets.hpp. Command exited with code 1 This happened for me locally when I did the work, so I removed it from the superproject locally, and deleted disjoint_sets locally. Any thoughts on how I can tell the build to ignore disjoint_sets so it can install the headers from the new location and complete? This is a temporary situation until the superproject is updated, but the superproject cannot be updated until the code is merged into graph, and the builds are all failing so I cannot prove to the graph maintainers that the pull request is viable. The only way I can see around this is to rename the disjoint_sets headers from pending and into graph, and then fix up graph and graph_parallel, but my intention was to just merge the header into graph, not to change the location of delivered headers. That said, getting something out of pending is always a good thing. Any other ideas? Thanks, Jim

2 1

Making two Boost libraries interoperate
by Andrzej Krzemienski 26 Apr '19

26 Apr '19

Hi Everyone, Somewhat in connection with the discussion about modularizing Boost libraries, we had a certain conceptual problem recently about providing a customization code that allows Boost.Serialization library to serialize Boost.Optional. Such customization requires some code to be written (template specializations provided). Conceptually, such customization code does not belong to Boost.Serialization: we do not expect that Boost.Serialization provides specializations for every library that someone might ever want to serialize. It would also require the maintainer of Serialization to keep track of the implementation of Optional. However, it also does not belong to Boost.Optional: we do not expect that Boost.Optional provides customization points for every framework out there that the users may want to ever use. It would also require the maintainer of Optional to keep track of the implementation of Serialization. However, it is a natural expectation of a Boost user that if the library offers two components they should just smoothly inter-operate with one another. We could provide a small module Serialization-Optional-interop, but that would require many such components to exist and be maintained by someone. I would like to obtain some guidance on how to address such issue. The same problem must already be present between other Boost libraries. Maybe this has been already brought up, and we have a policy for solving this problem somewhere? Regards, &rzej;

10 23

Google Summer of Code slots
by David Bellot 24 Apr '19

24 Apr '19

Dear Boost community, Google has allocated 11 slots for our summer students this year. It's a great news. It means that 11 brilliant students will have the opportunity to work full-time with us and contribute to our libraries. The selected students will be announced soon. I'd like to thank all the mentors for their hard work in preparing the proposals and helping the students to candidate. And of course, a big thank you to Google for supporting open source every year. Best regards, David Bellot

1 0

undefined behavior in Boost.Program_Options
by Chris Rorvick 24 Apr '19

24 Apr '19

I am seeing my GCC ubsan builds littered with "downcast of address xxxxxxxx which does not point to an object of type 'holder'" errors [3] coming from Boost.Program_options (Boost 1.69). The issue has been documented in various places [1][2] but I do not see anything on the mailing list in recent months; apologies if I have missed something. A workaround is proposed on the StackOverflow post [1]. Does anyone have any thoughts on this? Many thanks! Chris [1] https://stackoverflow.com/questions/38987728/why-does-boostany-exhibit-unde… [2] https://github.com/boostorg/program_options/issues/76 [3] .../boost/boost/any.hpp:249:17: runtime error: downcast of address 0x602000053610 which does not point to an object of type 'holder' 0x602000053610: note: object is of type 'boost::any::holder<std::string>' 6f 00 80 67 d0 91 ec 88 fe 7f 00 00 68 33 09 00 40 60 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^~~~~~~~~~~~~~~~~~~~~~~ vptr for 'boost::any::holder<std::string>' #0 0x7ffe8df13e3d in boost::program_options::typed_value<std::vector<std::string, std::allocator<std::string> >, char>::xparse(boost::any&, std::vector<std::string, std::allocator<std::string> > const&) const (redacted+0x28be3d) #1 0x7ffe88bb0cd5 in boost::program_options::value_semantic_codecvt_helper<char>::parse(boost::any&, std::vector<std::string, std::allocator<std::string> > const&, bool) const (.../libboost_program_options.so.1.69.0+0xdacd5) #2 0x7ffe88ba9193 in boost::program_options::store(boost::program_options::basic_parsed_options<char> const&, boost::program_options::variables_map&, bool) (.../libboost_program_options.so.1.69.0+0xd3193) #3 0x7fff0b727dbf in rdx::launch::OptionsWrapper<boost::program_options::options_description, boost::program_options::variables_map>::prepare(int, char**, std::vector<int (*)(boost::program_options::options_description&), std::allocator<int (*)(boost::program_options::options_description&)> > const&) (redacted+0x448dbf) #4 0x7fff0b755e80 in int generic_wrapper<std::vector<int (*)(boost::program_options::options_description&), std::allocator<int (*)(boost::program_options::options_description&)> >, rdx::Function<int (boost::program_options::variables_map const&), 56u>, rdx::launch::OptionsWrapper<boost::program_options::options_description, boost::program_options::variables_map> >(int, char**, std::vector<int (*)(boost::program_options::options_description&), std::allocator<int (*)(boost::program_options::options_description&)> > const&, rdx::Function<int (boost::program_options::variables_map const&), 56u> const&, rdx::launch::OptionsWrapper<boost::program_options::options_description, boost::program_options::variables_map>&) (redacted+0x476e80) #5 0x7fff0b76593c in redacted(std::string const&, int, char**, std::vector<int (*)(boost::program_options::options_description&), std::allocator<int (*)(boost::program_options::options_description&)> > const&, rdx::Function<int (boost::program_options::variables_map const&), 56u> const&) (redacted+0x48693c) #6 0x95c21d in main (redacted+0x95c21d) #7 0x7ffe82fb83d4 in __libc_start_main (/lib64/libc.so.6+0x223d4) #8 0x963523 (redacted+0x963523)

3 2

Re: [boost] CMake, modular Boost, and other stories
by Mike 24 Apr '19

24 Apr '19

> Hmmm - so no boost library should include any > other boost library? DoesÂ that seem a good idea? Please don't put words in my mouth. I didn't say that and you know it. But the dependency graph could easily be significantly simplified once c++03 is no longer a concern. Again: I'm talking about the future, not the current state. Just an example: [1]Boost.TypeErasure depends on [2]Boost.Thread(and all that entails), just because somewhere in its bowels it needs a mutex. > It's always been good practice to notÂ repeat/copy > functionality in one library into another. Not always. A recent example I stumbled over: Boost.Signal2 depended on boost multi index (which itself depends on a lot of other libs) because it reused it's scope guard implementation (IIRC about 50 lines of straight forward code). Tying yourself to another library for something trivial like that should not be a no-brainer. > But what is really needed - and it may already exist > in BCP but hasn'tÂ been promoted is a simple tool: > a) start with one's application > b) run the app through a tool which recurrsively > reads headers > c) and creates a list of all headers needed > d) extract library names from that list > e) add the git repo of those libraries to my apps > project. So boost should not only get its unique build system, but also its unique dependency management tool? I can tell you as a user: Thanks but no thanks. Also: Didn't you forget source files somewhere in there? What about tests? Bottom line: If boost as a whole was developed as a single project with some coordinated devlopment goal and strategy , it would make sense to distribute it as a single package/framework and a single cmake config file. It seems to me however, that it is more a (huge) collection of independently developed libraries, so I think it is more appropriate to treat them as such, even if there is a huge amount of coupling between them. Am 23.04.19, 23:56, Robert Ramey via Boost <boost(a)lists.boost.org> schrieb: On 4/23/19 2:28 PM, Mike via Boost wrote: > I for one very much hope that boost (at least the libraries that > are actively maintained) will become less coupled > in the future, such that when I just want to use > library X, the rest of boost doesnʼt come as a > dependency with it. Hmmm - so no boost library should include any other boost library? Does that seem a good idea? Itʼs always been good practice to not repeat/copy functionality in one library into another. Iʼve said it many times before so I wonʼt make a big deal about it here. But what is really needed - and it may already exist in BCP but hasnʼt been promoted is a simple tool: a) start with oneʼs application b) run the app through a tool which recurrsively reads headers c) and creates a list of all headers needed d) extract library names from that list e) add the git repo of those libraries to my apps project. I donʼt seen any way to get around this. And util we can easily do this - boost will not be modular. Robert Ramey _______________________________________________ Unsubscribe & other changes: [3]http://lists.boost.org/mailman/listinfo.cgi/boost References 1. http://Boost.TypeErasure/ 2. http://Boost.Thread/ 3. http://lists.boost.org/mailman/listinfo.cgi/boost

6 5

[doc][geometry][gil][signals] Broken links for Boost 1.70
by Mateusz Loskot 24 Apr '19

24 Apr '19

Hi, On https://www.boost.org/doc/libs/1_70_0/ links to these documentations are broken: https://www.boost.org/doc/libs/1_70_0/libs/geometry/index/doc/html/index.ht… https://www.boost.org/doc/libs/1_70_0/libs/geometry/extensions/doc/html/ind… https://www.boost.org/doc/libs/1_70_0/libs/gil/doc/html/index.html https://www.boost.org/doc/libs/1_70_0/libs/signals/ Could anyone help to identify what is going wrong with those and how to fix it? p.s. I considered posting to boost-docs but that list seems inactive. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

5 5

CMake, modular Boost, and other stories
by Mike 23 Apr '19

23 Apr '19

I'm very much in favor of separate packages. James is right, that - at the moment - most boost libraries are so tightly coupled that they can't really be treated as separate libraries, but when changing things it is just as important to ask, "Where do you want to go?" as "where you are now". I for one very much hope that boost (at least the libraries that are actively maintained) will become less coupled in the future, such that when I just want to use library X, the rest of boost doesn't come as a dependency with it. It also fits the management structure (or rather the lack thereof) much better. Also, the mechanisms for modular boost distributons already exist through e.g. vcpkg and conan, so I don't see the problem in also providing independent cmake configfiles. Finally: About how many libraries are we talking here anyway? Only the compiled ones get their separate config file - correct? Best Mike

3 2

[GSOC2019][Boost.uBLAS]
by swornim baral 23 Apr '19

23 Apr '19

Hi List, I realize the deadline has passed for seeking a mentor for GSOC, and I apologize for the delay in initiation. I came to know about the program two weeks prior to the deadline, and started working on completing my proposal and competency test prior to finding any mentors. However, I am still very much interested in working on the project of adding a new numerical and multi-linear algebra algorithm to Boost.uBLAS library. I would love to work on the algorithm for calculating Kronecker and Hadamard product with the guidance of a potential mentor. Since I submitted the proposal in a hurry and without any discussion with a mentor, I could not include specific implementation details in my proposal. Below is the link to my final proposal that I submitted for the GSOC 2019. I would really appreciate any feedback on the proposal, competency test and suggested reading materials to get a head start on implementing the algorithm from any interested mentors. https://drive.google.com/open?id=1saUedBfMCOpmVqQfn1a3YcfPtjPYLeDC . Sincerely, Swornim baral

1 0

Re: [boost] CMake, modular Boost, and other stories
by Peter Dimov 23 Apr '19

23 Apr '19

> Mike wrote: > > > Finally: About how many libraries are we talking here anyway? Only the > > compiled ones get their separate config file - correct? > > ~30-40 at last count. Yes, at the moment. More like 50. Some libraries install more than one.

1 0

[variant2] Formal review
by Bjorn Reese 20 Apr '19

20 Apr '19

I. DESIGN --------- The main design decision of Variant2 is the never-empty guarantee, which is relevant when replacing the value of a variant. This is done without overhead if the alternative types are "well-behaving"; if they are not, then Variant2 falls back to using double storage. This is a major difference to: * std::variant which enters an invalid (valuless_by_exception) state. While that may be appropriate for some use cases, there are others where it is not. For instance, the variant may be used for a state machine where the alternative types are function object types to be invoked when events arrive. Having a valueless state is the wrong choice for this use case. * Boost.Variant which uses a temporary heap object instead. Avoiding this internal heap allocation is sufficient grounds for another never-empty variant type. In time critical applications heap allocation not only introduces indeterministic timing, but may also incur priority inversion due to thread synchronization within the heap allocator. Variant2 has several ways to ensure the never-empty guarantee: V1. If all alternative types have non-throwing assignment, the variant cannot fail during re-assignment. V2. If an explicit null state is available, then this is chosen on re-assignment error. This is similar to std::variant, except is is opt-in. V3. If one of the alternative types has a non-throwing default constructor, then this is chosen on re-assignment failure. V4. Otherwise, the variant will remain it its old state (due to double storage) if re-assignment fails. Criterion V3 is possibly surprising because the variant may change to another type not anticipated by the user. This should be opt-in instead (e.g. using a tag.) I am missing a function to get the index of a type to work with the index() function. Something similar to holds_alternative() but that returns the index instead of a boolean. This useful in switch statements, when we want to avoid visitors for some reason: variant<int, float> var = 1; switch (var.index()) { case index_of<int>(var): /* Do int stuff */ break; case index_of<float>(var): /* Do float stuff */ break; } It would also be beneficial for performance reasons to add accessors that have a narrow-contract, similar to relaxed_get() in Boost.Variant. The implementation is already there (detail::unsafe_get.) Better compiler error messages would be desirable. For instance, if we use an illegal visitor that has different return types, then the compiler error does not give us any hint about the different return types. II. IMPLEMENTATION ------------------ The implementation is high quality. Although it does lots of meta-programming, most of the style is simple and easy to follow, especially if you have a rudimentary knowledge of Boost.Mp11. In a few places, like the visit() return type, the meta-programming is more hardcore. variant<T...> defines _get_impl as a public "private" function. This can be made more safe by using detail::unsafe_get instead of _get_impl throughout the code. detail::unsafe_get will continue to call _get_impl, but the former should be made a friend of variant<T...> such that _get_impl can be made private. The other public "private" function, variant<T...>::_real_index(), does not seem to be used and can be removed. The emplace_impl(mp_false, mp_false, ...) contains two distinct cases that depend on a compile time condition. If this is split in two, then the two assert()s can be changed into static_assert()s. The variant_alternative and get functions have a couple of compiler workarounds. The code could be made clearer if the workaround is always used for all compilers. Or does is this related to C++11 constexpr? III. DOCUMENTATION ------------------ The documentation is mainly aimed at experienced users. There is no tutorial for people unfamiliar with variant types, nor is there a design rationale that explains why Variant2 is exists when we already have Boost.Variant and std::variant. The reference documentation is adequate, although a bit terse. IV. MISC -------- Having written my own variant class (that has a maximum size, and any type exceeding the limit is allocated on heap) puts me in a good position to assess Variant2. I was also the review manager of Boost.Mp11 upon which Variant2 is built. I have spent 5-6 hours reading documentation, reviewing the code, and writing small test programs. V. VERDICT ---------- Variant2 fills a hole not covered by Boost.Variant and std::variant. I vote to CONDITIONALLY ACCEPT Variant2 into Boost, provided that the following change be made: 1. The selection of an arbitrary non-throwing type in case of an re-assignment failure (criterion V3 in the DESIGN section above) should be made optional. By default it should use double storage in this case. I would furthermore like to see improvements to the documentation, as well as the index_of/safe_get functionality, but neither is a requirement for acceptance. I have not reviewed expected<T, E...>.

11 29

[boost-ci] Build failures for repositories using boost-ci
by James E. King III 19 Apr '19

19 Apr '19

Recent changes to boost have exposed some shortcomings in the boost-ci infrastructure, specifically the use of CXXFLAGS as a variable to hold b2-specific "cxxflags=" content is now getting passed through to the bootstrap build and going to the compiler, and failing. I'm aware of the issue and I am working on a fix that will be backwards compatible with existing Travis CI scripts that use boost-ci to drive their builds. There may also be changes for Windows, but I haven't looked at that yet. This affects the majority of the CMT repositories as well as date_time, format, uuid, function, move, and signals2, and possibly others. More information to follow... - Jim

1 1

[serialization] clarify in doc on overview that library does not aim for inter-process communication nor for backward compatibility
by rafalcpp＠peerfreedom.org 18 Apr '19

18 Apr '19

Hello, Some developers expect archiving or serializing libraries to be backward compatible, for example if I simply save vector<string> to a JSON, then files written from program with more modern json library will be readable on older one and vice-versa. Boost serialization is instead rather intended to read files created by same program with same boost version (or read it on a more recent, but not on older, version of boost). Could we clarify this with a warning on the Overview page? Perhaps something along this lines: " Warning: please note that the format version may change with boost.archive library versions, an old program may not be able to read a format that was designed after it was build. Explanation: some archive libraries offer long lasting forward and backward compatibility of the archived data. For example if your program saves list of book titles into a JSON file, then if your main program itself does not change you can expect to always be able to load that json file - even when loading it on old version of JSON library while archive was saved on a very new one. This is however *not* the case for this boost archive library (at least for the default archive classes) - here even if your main program stays the same then archives written on one using more recent libboost might be unreadable on ones using older libboost. This also means that communication between users (e.g. over Internet) by exchanging archives created by this library will not work in case if users build the program on their own and build it against different versions of boost. Although, a work around exists in form of including specific version of boost serialization library, and freezing that version, in your program, if you are willing to stick to one version of this module. " Please correct if there are any mistakes (for example if that is possible in some special way).

2 1

[variant2] Review
by Jan Herrmann 17 Apr '19

17 Apr '19

Hello, I looked at the review, at the code and some time ago I tried to implement my own variant. In my opinion in variant2 the individual parts are more worth than the whole. Most implementation details would be of great use for implementing variants with a differnt trade-off. Hence the library ought to be split into several independend parts: * a typing switch * a variadic union * an extendable visitation mechanism * a variant view * related type traits * several implementation of a concrete variant 1. A typing switch The typing switch would be provide a litle bit more than (and can be implementated with help of) mp_with_index. The following pseudo code shows the implementation idea: template<size_t MaxIndex, class Function, class Cast, class Object> constexpr decltype(auto) typing_switch(size_t index, Function fun, Cast cast, Object obj) { return fun(cast(integral_constant<size_t, index>{}, obj)); } The object is a variant and the cast transfroms this special variant to a concrete value (with type). The function is provided by the variant user. The visit function (line 1732) would become something like this: template<class Variant> struct variant_cast { template<class Index> constexpr decltype (auto) operator()(Index, Variant& V) { return unsafe_get<Index::value, V>(); } }; template<class Fun, class Variant> constexpr decltype(auto) visit( F&& f, V1&& v1 ) { return typing_switch<variant_size<V1>>(v.index(), f, variant_cast<V1>, v1); } A simplified deserialisation can be implementated as follows: template<class Types> struct index_to_type { template<class Index> constexpr decltype (auto) operator()(Index, std::nullptr_t) { return mp_identity<mp_at<Types, Index>>{}; } }; template<class Variant, class Archive> Variant deserialize(Archive& ar) { size_t index; ar >> index; Variant f = [&ar](auto type) { decltype(type)::type concrete_element; ar >> concrete_element; return Variant{std::move(concrete_element)}; }; return typing_switch(index, f, index_to_type<Variant>{}, nullptr); } With help of this function an implementation of a visitation function is easy. 2. A varidic union Without doubt a type implementing a varidaic union is a building block for almost every variant implementation. It should be part of the public interface, well tested and with a minimal interface (get and emplace) 3. An extendable visitation mechanism This could be used to implement visitation on multiple different variants. It should use visit on one variant as customization point. 4. A variant view (and a mutable variant view) It could have the following form: template<class... T> class variant_view { void* value; size_t index; public: /* visit ... */ }; It is a little bit like folly/DiscriminatedPtr.h (https://github.com/facebook/folly/blob/master/folly/DiscriminatedPtr.h) but without platform specific code. It can be used for functions which take variants as a const references (or in the mutable form as variants which can change the value but not the actual type). It can be constructed from corresponding variants, values (which are part of T...) and other variant_views. As long as it is constructed from a variant implemented with the variadic union the process can be simple: all members of a union have the same address as the union and the index is equal. For special cases the process can be more complicated. For other variant_views the transformation can be implemented as a runtime lookup in an array and for simple values it is simple. A variant_view can for example be used for functions accepting const references like output and serialisation, or for referencing "polymorphic" objects like nodes in ASTs. 5. Related type traits Meaningfull type traits which can be used in one variant have a good chance be be used in a related one. If one variant want to static assert in case void is one of its types the logic is probably usefull for others. They should be collected. 6. Several implementation of a concrete variant This is the place for variant2. With this building blocks it should be simpler to implement a custom variant. Now lets think of a few use cases: A class contains 3 variants each containing only a few "small" types. Instead of using 3 variants it could pack all indices into one int and construct variant_views as needed. This can reduce the size of the class and saves memory bandwidth. Editing of variants would be of course more complicated. A variant containing a few trivial small types which are used in allmost all cases and one type (T_evil) which is used rarely, is big and can throw in certain situation. The soloution can be a normal variant with the exception of storing T_evil as a smart pointer and dereferences it when visited. A variant with allocator support. In case a user has a solution (or idea) for their variant which lives in shared memory a simple blueprint with generic components like varidic union, a typing switch and useable type traits may be of help. I think requirements for different variant types mentioned in the review could be implemented with some well defined basic building blocks. Beside these thougths I looked at the library. expected.hpp: I tried to compile the following file (containing only one non empty line): #include <boost/variant2/expected.hpp> and it does not compile. It should be a self-contained header. Therefore it should be not part of the library. variant.hpp: Personally (in contrast to other reviewers) I would prefer code more structured in different files. In an ideal world there is for every component a single header file (in clean C++ 17) with minimal dependencies which directes for compiler (and version) specific stuff to a different header. For the future it would result in source code written in newest standard without disturbing influence from ifdefs caused by old buggy compilers. The source has more than 1800 lines with only a few comments, short (1 char) names and very long lines (200 chars and more). For me it is not easy to read (after clang-format it is 2030 lines). Variant alone has more than 450 lines of code. With more shorter files the connection of (and dependencies among) the components would be more visble. I started at the begining of the file and searched for a testcases for monostate and I didn't found one. There are a few testcases inside variant_valueless.cpp which use monostate but none which test it directly. Next variant_size. There are testcases but most deal with variants of type 'variant<> const', 'variant<void>' and the like. Declaring variables of these types results in compile time errors. It is not wrong std::variant gave me the same result, but it is a kind of strange that most tests are implemented in terms of variants wich are ill-formed. On the other hand there are no tests which do not compile. These are two example which should not compile. The template detail::variant_alternative_impl looks like something which copies const, volatile and references. Is there a difference to copy_cv_ref at the end? Could it be used? At the end of the file the comparison is implemented. But operator!= is not implementated in terms of operator== and operator<= and others not in terms of operator<. In case there is a reason for it documentation would be nice. Summarized I think variant2 should NOT be part of boost. I think the focus should be more on reusable components and better documented code. I think most of the code could be very usefull with more descriptive names and test. Regards Jan Herrmann

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[variant2] Review of Variant2 started today : April 1 - April 10
by Michael Caisse 16 Apr '19

16 Apr '19

The Boost formal review of Peter Dimov's Variant2 library will take place April 1 - 10, 2019. Please consider participating in this review. The success of Boost is partially a result of the quality review process which is conducted by the community. You are part of the Boost community. I will be grateful to receive a review based on whatever level of effort or time you can devote. Variant2 is a never-valueless C++11/14/17 implementation of std::variant. >From the README: The class boost::variant2::variant<T...> is an almost conforming implementation of std::variant with the following differences: * A converting constructor from, e.g. variant<int, float> to variant<float, double, int> is provided as an extension; * The reverse operation, going from variant<float, double, int> to variant<int, float> is provided as the member function subset<U...>. (This operation can throw if the current state of the variant cannot be represented.) * variant<T...> is not trivial when all contained types are trivial. To avoid going into a valueless-by-exception state, this implementation falls back to using double storage unless * one of the alternatives is the type monostate, * one of the alternatives has a nonthrowing default constructor, or * all the contained types are nothrow move constructible. If the first two bullets don't hold, but the third does, the variant uses single storage, but emplace constructs a temporary and moves it into place if the construction of the object can throw. In case this is undesirable, one can force emplace into always constructing in- place by adding monostate as one of the alternatives. You can find the source code here: <https://github.com/pdimov/variant2> The master branch will be stable for the review: <https://github.com/pdimov/variant2/tree/master> Find the documentation here (also stable during the review): <https://pdimov.github.io/variant2/doc/html/variant2.html> Note: The repository contains an expected implementation also; however, that is not being considered in this review. Please provide in your review information you think is valuable to understand your choice to ACCEPT or REJECT including Variant2 as a Boost library. Please be explicit about your decision (ACCEPT or REJECT). Some other questions you might want to consider answering: - 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 which compiler(s)? 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? More information about the Boost Formal Review Process can be found here: <http://www.boost.org/community/reviews.html> Thank you for your effort in the Boost community. Happy coding - michael -- Michael Caisse Ciere Consulting ciere.com

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Mother of all Variants
by Nikita Kniazev 16 Apr '19

16 Apr '19

I do not see any progress in the never-ending never-empty vs everything discussion. It looks like an argument about tastes, and I see no room for compromise here. Number of examples for any point of view is also close to zero. Instead of saying that you would like more one or another, just implement it, and let the user decide which one to use. Or, at least, make a poll that will show needs in promoted by you implementation instead of forecasting from your big, but personal experience. A policy-based design is good in theory, but what in practice? In practice, you want one person to make and maintain bunch of different variants, which you, most likely, will never use, but users, most likely, will have nightmares in using it, especially in API, due to signature verbosity. More code will hurt preprocess and compile times for sure. What surprises me a lot that there was not much attention to the fact that because of number 2 in the name users will come and will ask about it. Do I need an upgrade? Is `variant` deprecated? Is `variant2` an improved version of `variant`?

1 0

GSOD
by Siddhartha Sen 16 Apr '19

16 Apr '19

Any information on how and where to apply for GSOD?

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[variant2] Andrzej's review
by Andrzej Krzemienski 16 Apr '19

16 Apr '19

Hi Everyone, I recommend that variant2 should be REJECTED in its current shape. The main (and only) reason for rejection is the never-empty basic exception-safety guarantee offered and endorsed by the library. I have serious concerns that by adding it into Boost we would be leveraging the concept that is bug prone and encouraging bad habits. I have expressed my concerns in detail in another mail. I find this to be in contrast with what I perceive as goals of Boost. It is my understanding that the never-empty basic guarantee is the core of the library therefore the conditional acceptance would not work. My recommendation would be different if the library dropped the goal of providing the never-empty guarantee, or if it provided a strong guarantee in the cases where assignment emplacement required to change the alternative. I honestly appreciate the work Peter has done to provide this library, but I strongly disagree with the primary design decision. If the library is still accepted I recommend the following things: 1. Call it something slightly different so that at least namespace name clearly indicates that it is not an "improved std::variant" or "improved boost::variant" but just another offer in the market with different design choices in the design space: maybe ne_variant (for "Never Empty") or si_variant (for "Strong Invariant"), or even pdimov_variant (for "Perfectly Defined Invariant Model Of Variant"). 2. Drop the implementation of std::expected. It does not fit into the same library even if 90% of the implementaiton is shared. Propose a second library even if what it does is to #include the variant. 3. Move functions unsafe_get() from namespace detail and make them part of the official interface. You need to use them yourself in the implementation of visit() because otherwise you could not implement it efficiently. They are part of the minimum efficient base interface. Even if required very occasionally. 4. Provide a 2 minute introduction to the library for the newbies. We do not need a full tutorial. A link to someone else's description will do, but a short introduction I think is a must. I offer to help write one. 5. Provide a design rationale explaining why the never-guarantee is offered at all and why in this way. Why you are disregarding the design choices of boost::variant's never-empty guarantee. Also provide a detailed description on which algorithm is chosen under what circumstances and what it does to provide the guarantee. Now, to review questions: - What is your evaluation of the design? As noted, I strongly disagree with the main design choice of the library: the never-empty guarantee. I see no positive value, I see negative value. This aside, I do not see much design choices here: it is a quite small vocabulary type. - What is your evaluation of the implementation? Of all reviews I have participated in I have never found it so easy to understand the implementation. I find it very clean and short. I appreciate that it is a single header library. I can just copy the content of the file and test it in WandBox. Also the implementation is a very good practical tutorial on mp11. Peter already wrote good tutorials on mp11, but here for the first time I have seen it used for something that I consider a real life application. The implementation of variant looks so simple with mp11. - What is your evaluation of the documentation? The reference part meets the high standards of Boost. I am missing even a short introduction that would give us the motivating example. Some have said that it is enough to say "find the tutorial on std::variant". I disagree: there is no good introduction to variant, and I think Boost libraries have a good history for providing a good problem domain description apart form the implementation. I also think that given the controversies around the never-empty guarantee the design choice requires a detailed information in the docs. - What is your evaluation of the potential usefulness of the library? Given that I find std::variant design superior, I suspect this library would be useful in environments that cannot afford to use C++17 yet. It has advantages over boost::variant. It has cleaner implementation. boost::variant is giving me lots of warnings in clang-tidy. I expect these to be gone in variant2. Also the trade-offs made in double buffering may be superior to those in boost::variant: no memory allocation, no additional potential reason for throwing. - Did you try to use the library? With which compiler(s)? Did you have any problems? I tried to break the library with nasty cases in various clang and GCC versions. I reported some minor bugs over GitHub. Peter is quickly addressing them. The library does not compile in GCC 8.2 and higher in C++17 mode due to some bug in GCC. This is already tracked as issue. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I have spent a number of evenings reading the docs, the sources, playing with the library, debugging, discussing the design in the mailing list. I also followed the discussion in the C++ Standards Committee, where similar issues with never-empty guarantee were discussed. - Are you knowledgeable about the problem domain? I have a lot of experience with different implementations of `optional`: I am maintaining the boost version, I have provided the wording and the design for the std version and provided the reference implementation thereof (at https://github.com/akrzemi1/Optional/) which turned out surprisingly popular. Optional needs to solve similar problems in the implementation: manually managing a raw buffer or a union, and has similar problems with exception safety guarantees. However it does not need to address the never-empty guarantee issue. I also use a lot of boost::variant at work. Finally, I want to thank Peter for writing this library and submitting it for review. The review itself was very instructive. Regards, &rzej;

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[doc][test] change log broken from release notes
by Raffi Enficiaud 15 Apr '19

15 Apr '19

Hi, The link to the change logs is broken from the 1.70 release note (points to https://www.boost.org/users/history/libs/test/doc/html/boost_test/change_lo… instead of https://www.boost.org/doc/libs/1_70_0/libs/test/doc/html/boost_test/change_… ) I believe I used the same way I did for the past releases. How can I correct this? Thanks, Raffi

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Re: [boost] [boostorg/python] Building against multiple python implementations broken on 1.70 (#262)
by Stefan Seefeld 15 Apr '19

15 Apr '19

On 2019-04-14 7:50 p.m., Peter Dimov wrote: > > I'll need to look into this. Apparently, |FindBoost.cmake| solves this > by forcing the user to specify the version in |find_package(Boost > COMPONENTS python27)|, but the CMake configuration files installed by > 1.70 only take |find_package(Boost COMPONENTS python)|, so multiple > versions installed at the same time are a problem. > > In the meantime, you can add |--no-cmake-config| to your |b2 install| > command line to skip the installation of CMake configuration files, > which ought to give you the 1.69 behavior back. > This is *exactly* the kind of situation I was afraid of when I argued strongly against adding CMake support to my own projects: Before I had to deal with B2 issues that I had difficulties resolving myself. Now I have to deal with B2 *and* CMake issues, being even more dependent on others. That's not my definition of progress. Stefan -- ...ich hab' noch einen Koffer in Berlin...

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[variant2] never-empty guarantee considered harmful
by Andrzej Krzemienski 15 Apr '19

15 Apr '19

Hi Everyone, I waned to re-iterate my concerns regarding the never-empty guarantee provided by variant2 (as well as by boost::variant). Sorry for starting a yet another thread, but I think it necessary to cleanse, group and structure the information scattered among a number of threads. I think that the never-empty variant deceives people into thinking that it offers something useful and important, but in fact it does not, and more, it can encourage people to trust that they have some guarantee which they haven't, and owing to this to write buggy code. The solution that never-empty variant offers is similar to another common idea of replacing undefined behavior with *any *defined behavior whatsoever, and that is supposed to be "safe" because programmers no longer see symptoms of their bugs. Let me digress on the subject of UB for a second. UB is always caused by a bug in the program. Thus if the program had no bugs, it would have no UB. But many people are very afraid of UB per se, and less afraid of bugs. They will divert much attention to prevent UB at surprisingly high cost, but focus less on preventing their bugs. UB is a useful symptom of a bug and therefore can help detect and remove bugs, but people are sometimes so afraid of UB that they loose this connection to the extent that they are willing to remove the link between the two and get rid of potential UB even at the cost of concealing the bugs. And they consider it "safe". For instance, someone writes a sequence container class and faces the problem. I will need to provide access to elements by index, but people will give me bad indexes (because they can), this would be a UB, and I do not want a UB, therefore I apply a "safety" feature. Whenever someone gives me bad index, I will return a reference to the first element. Sure, it is surprising, and likely not what the caller wanted, but it is better than UB. And in case I have no elements in my container I will default-construct one in the container. Sure it is not nice to to increase the size of the container only because someone gave me the wrong index, but... *anything is better than UB.* I wonder if everyone reading this mail will agree with me that reasoning "anything is better than UB" is wrong. The author of this "safe" container calls his container "safe" because whatever bugs his callers have, they will never trigger UB *in his library*. Maybe in another library, at another level, but not in his component. In the end we will get programs that will cause self-driving cars to crash and kill people, space rockets to explode, but the "safe" program itself will never crash. Instead the author of the "safe" container should be focusing on something else. Why is my caller giving me the wrong index given that he can check my size and easily determine that this index is wrong? The answer is, the programmer probably intended to do something else and this needs to be brought to his attention. Tools like compilers and static analyzers cannot detect bugs in general because they cannot guess our intentions, but they can detect things like UB, so if we keep a correspondence between bugs and UB, we can detect bugs by detecting UB. This has been described in more detail in this paper: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1043r0.html (section 6). Now, the situation is similar with the never-empty guarantee of the variant that offers only a basic exception safety guarantee on assignment. Because the guarantee is basic (that is, it is not the strong guarantee), the only thing we can do with it in order not to risk program bugs is, following the Dave's article (https://www.boost.org/community/exception_safety.html) to either destroy or reset the variant that threw from assignment. And this is what correct programs do, and the technique is quite simple: unless objects provide strong exception safety guarantee (or some other guarantee that allows you to reason about the values of objects that threw) they should die in the stack unwinding process. The damage that the never-empty guarantee (implemented by setting unexpected values) does is to encourage people to think that with variant they can do something more than just destroy or reset. And while technically, variant itself is "clean" in this case (it really doesn't invoke UB itself) it causes the code that is using it to be incorrect. Two examples. I may have the following instance: ``` variant2<X, Y, shared_ptr<Z>> v {X{"params"}}; struct Visitor { int operator()(shared_ptr<Z> const& z) { return z->getCount(); } int operator()(X const&) { return 1; } int operator()(Y const&) { return 1; } }; ``` Where X and Y have nasty properties (are declared to potentially throw from move constructor and do not have default constructors). My v could technically store a null pointer at some point. In the visitor I do not check for this eventuality. Someone could say, "you should always check for null pointer, because anything is better than UB", But I know I never will be storing a null pointer there. I use shared_ptr for its ability to share ownership of an object, not for its ability to be null. I guarantee that I will never set the shared_ptr<Z> alternative to nullptr value. Therefore in the visitor I can assume that the pointer is never null. But if I am encouraged by the variant's never-empty guarantee to depart from Dave's guidance not to trust basic-guarantee objects that threw, I may end up in the situation where I start with alternative X, I want to assign alternative Y, but it throws, and because the only type with the default constructor is shared_ptr<Z>, I will get a nullptr value which I never intended. This is not bad yet. But now, if I apply my visitor on my variant, my precondition that the pointer is not null will be violated: ``` variant2<X, Y, shared_ptr<Z>> v {X{"params"}}; BOOST_SCOPE_GUARD(&v) { visit(Visitor{}, v); }; v.emplace<Y>("params"); // throws ``` Now, variant2 fulfills its guarantee: it stores one of the alternatives (of arbitrary choice and arbitrary value), but it injected me the worst possible value of the type with the weak invariant. Thus, variant2's invariant may be strong, but it exploits the weak invariants of the types of the alternatives. And unfortunately, a lot of types, even in the STD, have weak invariants and use the default constructor to set the degenerate state. Thus, my program has UB, and hopefully a crash, because I was deceived by the never-empty guarantee: I thought it would be "safe" to observe such variant that threw. Second example comes from Peter: ``` template<class T> class monitor { T const& v_; T old_; public: explicit monitor(T const& v) : v_(v), old_(v) {} ~monitor() { if( v_ != old_ ) std::clog << "value changed"; } }; ``` Suppose I use it like this: ``` { variant2<X, Y, shared_ptr<Z>> v {shared_ptr<Z>{}}; // let me check if this code sets the v to a non-degenerate value: monitor m {v}; v.emplace<X>("params"); // succeeds v.emplace<Y>("param"); // fails: null pointer set. } // no value change reported ``` although the only state changes I initiated in this block were to set types X and Y, I got the wrong result from the monitor, because the "safe" guarantee of the variant chose some state that corrupted the monitoring logic. variant2 delivers its guarantee as promised: some value is there, but my monitoring is compromised because of its arbitrary choice of value. Note that std::variant does not have this problem: a distinct state is set upon such exception that is always different than any value of any of the alternatives. Of course, this second example has problems of its own. It assumes you can invoke operator== on an arbitrary T of which we know nothing. It assumes that T's invariant allows the values to be compared, but this is not correct an assumption. Type T can have a weak invariant: one that does not even allow comparing two values. You cannot just invoke arbitrary operations on an unknown T in the destructor, if you do not know they exception safety guarantees. T's comparison could potentially throw. Even destructors of generic components such as vector<T> or optional<T> in their non-trivial implementations only invoke operations on concrete types: pointers and bools, but for the T they only call destructors. Peter argues that a call to the operation on a variant could be invoked indirectly form the destructor: destructor calls function f(), function f calls function g(), function g() calls function f() and function h() makes a visitation on the variant. But can you see what this means? I am calling some function f() from the destructor, which is supposed to clean up resources, and I am not sure what f() does, if it does some hidden things beyond my control. This is a buggy code already. Now, to address another argument in favor of never-empty, arbitrary-value-choosing guarantee. Emil says that with never empty-guarantee we can more easily reason about the variant: it is *always* one of the alternatives: rather that "either one of the alternatives or some degenerate state. He argues that once we allow the faintest possibility for the degenerate state, we have to check for it *everywhere*. I think that the simple binary model, "either the weak state does not exist or is potentially everywhere", while it often works for many types is, not adequate to describe the reality of the variant. People need models (which are simplifications of reality) to help them manage complex reality. But models have the downside of not allowing people to see the reality beyond what the models allows them to see. We ave to distinguish "ordinary" weak state and "unusual circumstance" weak state. Types like unique_ptr or fstream have ordinary weak state: it is created by a constructor. Worse, by the default constructor, so if you just declare the variable name and forget about parameters you immediately get the weak state. It is easy to obtain this state. And therefore in many places we need to be prepare to handle them. But other types (which we have fewer in STD: only std::variant, I think) can have only "unusual circumstance" weak state: you cannot initialize the object to contain this state (unless you move/copy construct from another object that already has one). You can only get it in situations that for other reasons require special caution from programmers. I am aware of two: * when an object is manually moved from (by explicitly casting an lvalue to an rvalue reference, which std::move() does) * when a mutable operation on an object with basic exception safety guarantee threw an exception. In the first situation, in a generic context where we work with an unknown type T, after the move an object is in a valid but unspecified state. Type T is allowed to have a very weak invariant: so weak that even operator== may not be allowed to be invoked. In this state the only correct thing we can do is to either let the object die or reset its value (the only common way for resetting the value for different types is assignment of a non-degenerate value). Working under the assumption that programmers are aware of these constraints and are willing to adhere to them, we get confidence that these moved-from values will not be observed. (Of course this does not apply to types which choose to guarantee more after move.) We can design a resource-handling type, such as a socket, whose default constructor acquires the first available port, and leaves the object in a "strong" state, ready to work. there is no way to initialize objects of this type to a degenerate value. but if these sockets are move-constructible, the moved from object will have to store the degenerate value. But it would be pointless to check it anywhere in the program. We could only see it if programmers did not adhere to the rule, "only assign to or destroy the moved from objects, unless you know your object offers more guarantees". If programmers do not adhere to this rule, rather than covering up for their bugs, socket should make the UB as explicit as possible in order to assist static analyzers and tools in detecting such programmer's misuse of the moved-from state. Similarly with the after-throw state from the basic guarantee operation. The language cannot enforce this, but programmers are required to adhere to the rule: the only correct operations to be invoked in that case is to destroy the object or to reset it. again, if programmers do other things this is a bug and the type should try to reflect that in a controlled UB, rather than pretending that everything is fine and causing bugs later in unpredictable places, as was shown in the examples above. Insisting that unusual-circumstance weak state should be checked *everywhere* is depriving oneself of the ability to see the engineering trade-offs clearly. We do not have to distinguish "ordinary" and "unusual-circumstance" weak states in most of other types (nearly all types) because they do not pose so many implementation difficulties as variant does: implementing never empty guarantee costs too much in terms of run-time or spatial efficiency. For the sake of the simplicity of the model we cannot sacrifice too much efficiency. Given that efficient implementation of variant does not fit into the simple model, "either I have a strong invariant or not", one option is to provide a misleading and/or never-empty guarantee. But another option is to acknowledge that the simple model is no longer sufficient, and adapt a new one: more complex but one that better reflects the reality: we have two invariants: one that applies in normal code (where every function can be freely called and a weaker one that applies in circumstances that already require special caution from programmers. This is the C++ way: we deal with UB which some other languages do not have at all:this is more complex a task but allows for faster binaries and better bug detection. In a similar vein paper "Fixing Relations" ( http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1248r0.html) has been recently adopted in the C++ Standards Committee. The proposal compromised a nice and simple mathematical model, but this part of the model stood in a way to use some STL algorithms efficiently. C++ is not an easy language, and by trying to make it appear simpler than it is, we might only confuse the new programmers. One more thing, it is not the surprising value that variant2 may set upon the exception that bothers me the most. It is rather that indirectly it encourages programmers to think that it is fine or "safe" to read the value of the object that has been moved from or that threw from the basic-guarantee operation. We do not want to suggest that. Finally, all the above reasoning would not apply if variant offered a strong guarantee on assignment/emplacement for cases where the alternative needs to be changed. In that case: 1. It is perfectly fine to observe the state of the object that threw. 2. No surprising, potentially weak-state, value is ever fabricated in this case. Regards, &rzej;

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update of release notes for boost-1.70.0
by Oliver Kowalke 15 Apr '19

15 Apr '19

Hi, I've added 3 pull requests for boost/website... could you apply the patches and re-create the release notes for boost-1.70.0, please?! ty, Oliver

1 0

Re: [boost] [boostorg/python] Building against multiple python implementations broken on 1.70 (#262)
by Stefan Seefeld 15 Apr '19

15 Apr '19

On 2019-04-14 7:50 p.m., Peter Dimov wrote: > > I'll need to look into this. Apparently, |FindBoost.cmake| solves this > by forcing the user to specify the version in |find_package(Boost > COMPONENTS python27)|, but the CMake configuration files installed by > 1.70 only take |find_package(Boost COMPONENTS python)|, so multiple > versions installed at the same time are a problem. > > In the meantime, you can add |--no-cmake-config| to your |b2 install| > command line to skip the installation of CMake configuration files, > which ought to give you the 1.69 behavior back. > This is *exactly* the kind of situation I was afraid of when I argued strongly against adding CMake support to my own projects: Before I had to deal with B2 issues that I had difficulties resolving myself. Now I have to deal with B2 *and* CMake issues, being even more dependent on others. That's not my definition of progress. Stefan -- ...ich hab' noch einen Koffer in Berlin...

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[variant2] Review
by Damian Jarek 14 Apr '19

14 Apr '19

> - What is your evaluation of the design? Variant2 is clearly a superior replacement for the original variant type in boost - Boost.Variant and would be very useful for libraries in Boost and outside of it that are stuck on C++11/14. I strongly believe that triviality propagation should be supported, especially if Variant2 is to be used as the implementation detail of a type like `expected`. As for the hot topic of valuelessness - based on my experience of how variant types are typically used, I think that an implementation should loudly object at compile-time to any operation that could put it in a valueless state - e.g. if emplacing can throw and the type does not have a noexcept move constructor. However, I see that it could be quite inconvenient for many users and I consider the fallback mechanism currently in variant2 to be a good enough compromise. > - What is your evaluation of the implementation? I reviewed the implementation and it looks great. As a test, I replaced the internal variant type in Boost.Beast(beast::detail::variant) with variant2 to compare it against the private lean variant and against std::variant. In terms of compilation time, I've observed no significant difference between std::variant and variant2 when compiling the Boost.Beast test suite. Both were about 10% slower to compile than beast::detail::variant, which can be attributed to the additional header material which must be parsed by the compiler. In terms of runtime performance, I have not observed a significant difference between the 3 variants in terms of requests/second in a test project I use to optimize Boost.Beast performance. Note that Boost.Beast HTTP serialization makes heavy use of a variant to enable sending an HTTP message in as few write calls as possible. As far as I know, all types stored in the variant were "well behaved", so it did not test the double-buffering cases. > - What is your evaluation of the documentation? The documentation is adequate, however, it could use a few examples for users unfamiliar with the concept of sum types. > - What is your evaluation of the potential usefulness of the library? It is a useful replacement for Boost.Variant in C++11/14 libraries both in Boost and outside of Boost. > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? About 6 hours, most of which where spent on the compilation and runtime benchmarks based on Boost.Beast. > - Are you knowledgeable about the problem domain? I have implemented and used a few variant implementations in embedded code. I have also reimplemented the private and lean beast::detail::variant type on top of Boost.mp11. Conclusion: I recommend that Variant2 is CONDITIONALLY ACCEPTED if: - documentation is extended with usage examples - triviality propagation is implemented

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[gil] Boost.MPL replaced with Boost.MP11
by Mateusz Loskot 14 Apr '19

14 Apr '19

Hi, FYI, Boost.GIL switched from MPL and TypeTraits to MP11 (thank you Peter Dimov!) and C++11 <type_traits>: https://github.com/boostorg/gil/pull/274 This is a significant refactoring and as such it may have introduced bugs. GIL tests coverage had not been 100% and despite we've added numerous new tests, it's still far from complete. Any GIL users out there, if you notice any bugs, please let us know by opening new issue at GitHub or posting to to https://lists.boost.org/boost-gil/ Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

1 0

New B2 version, and CI failures.
by Rene Rivera 14 Apr '19

14 Apr '19

As some of you may have noticed, there were some changes to B2 yesterday (4-12). As previously mentioned I merged the start of the B2 C++ engine port to the develop branch. That change included some "improvements" to the building of the B2 executable. One of those improvements may be causing people CI failures. The new build scripts for B2 now respect, and use, the CXX and CXXFLAGS environment variables. As such it means that if you have those set for other reasons it may confuse the B2 build (i.e. bootstrap.sh/bat invocation) and fail that build. If that's the case you will need to clear those variables before invoking boostrap.sh/bat or build.sh/bat. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net

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[ASIO] 1.70.0 async_read_until reports undefined symbol with MSVS 2010
by Kenneth Porter 14 Apr '19

14 Apr '19

The following test code (inside #if 1) generates a LNK2019 (unresolved external symbol) with 1.70.0 but links successfully with 1.69.0. Inspecting read_until.hpp, I suspect the problem is with the enable_if expansion being too complex for the older compiler. (Hence the #if0 code which tests the individual conditions, but those seem to work fine.) The same code links with VS2019 and VS2015, and this linked under the previous Boost with VS2010. int _tmain(int argc, _TCHAR* argv[]) { typedef boost::asio::streambuf buftype; #if 0 const bool v1 = boost::asio::is_dynamic_buffer_v1<typename boost::decay<buftype>::type>::value; const bool notv2 = !boost::asio::is_dynamic_buffer_v2<typename boost::decay<buftype>::type>::value; #endif #if 0 void* cond = boost::enable_if< boost::asio::is_dynamic_buffer_v1<typename boost::decay<buftype>::type>::value && !boost::asio::is_dynamic_buffer_v2<typename boost::decay<buftype>::type>::value >::type* 0; #endif #if 1 boost::asio::io_service ios; boost::asio::ip::tcp::socket socket(ios); boost::asio::streambuf buf; boost::asio::async_read_until(socket, buf, '\n', NULL); #endif return 0; }

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[variant2] Review (comparison with other variants)
by Antony Polukhin 14 Apr '19

14 Apr '19

Hi, > - What is your evaluation of the design? Variant2 is very close to the boost::variant and std::variant. The major difference is in treating very rare border case. Let me put it very clear: * I really like the valueless_by_exception() approach of the std::variant. It gives perfectly determinated result in case of an exception during variant assignments, does not dynamically allocate storage and does not double the size of the variant variable. * The approach of existing boost::variant is not perfect. Exception during assignment could lead to the default construction of some type that was not previously held in the variant. This is actually a very creepy behavior: variant<foo, foo2, locked_mutex> v; v = foo2{}; // may suddenly lock a mutex via locked_mutex{} But users do not complain about this. Exceptions during assignments are so rare, that they just don't get hit by the issue. You have to try really really hard to get into the valueless_by_exception() state. The other drawback of boost::variant is that it dynamically allocates memory in some cases that are also quite rare. * Variant2 fixes the second drawback of boost::variant (dynamic allocations). But the first one is still there - in exceptional cases it may default construct something unexpected. Variant2 also may get performance issues because of the doubled size. Smaller data structures better fit the CPU caches. Some platforms allow returning small variables in registers (not on the stack). On some platforms addressing the first ~127 bytes of the structure is more efficient than addressing the other bytes. Increasing the size of a variant2 for dealing with cases that mostly never happen seems unreasonable to me. I'm not saying that the current boost::variant is perfect in border cases (it is not!). I'm saying that std::variant has no such drawbacks at all. Variant2 keeps some issues of the boost::variant and adds new ones. > - What is your evaluation of the implementation? Looks great. Enjoyed it. > - What is your evaluation of the documentation? Did not read very carefully. > - What is your evaluation of the potential usefulness of the library? Useful only if it will get as good as, or better than std::variant. > - Did you try to use the library? With which compiler(s)? Did you > have any problems? Have not used it. > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? Quick reading. > - Are you knowledgeable about the problem domain? Yes. I maintain the boost::variant and keep an eye on std::variant implementations. Conclusion: I would recommend to REJECT the Variant2 library in it's current state. My opinion would change if the underlying design changes in favor of explicit valueless_by_exception() state. -- Best regards, Antony Polukhin

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Re: [boost] [variant2] Formal review
by Bjorn Reese 14 Apr '19

14 Apr '19

On 4/13/19 7:26 PM, Bjorn Reese via Boost wrote: > Better compiler error messages would be desirable. For instance, if we > use an illegal visitor that has different return types, then the > compiler error does not give us any hint about the different return > types. A possible solution is to declare a tag and use this in the else-part of mp_if. E.g. struct return_types_must_be_the_same; template<class L> using front_if_same = mp11::mp_if<mp11::mp_apply<mp11::mp_same, L>, mp11::mp_front<L>, return_types_must_be_the_same>;

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crc.hpp:569 msvc warning C4800
by Kenneth Porter 13 Apr '19

13 Apr '19

<https://github.com/boostorg/crc/pull/2> Visual Studio 2010-2019 issue this warning for crc.hpp line 569: warning C4800: "'int' : forcing value to bool 'true' or 'false' (performance warning) bool const quotient = remainder & high_bit_mask; Replace with: bool const quotient = (remainder & high_bit_mask) != 0;

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[build] Bootstrap failures in Appveyor CI
by Andrey Semashev 12 Apr '19

12 Apr '19

Hi, I'm seeing multiple Appveyor job failures at bootstrap stage, here's an example: https://ci.appveyor.com/project/Lastique/winapi/build/job/qnu5dhfcpjx3vh1y The code did not change for quite a while and it was passing before. It first failed after the jobs were triggered by the 1.70 tag. Only some of the jobs have failed, and after I re-ran the jobs, a different set of jobs failed the second time. Is this something related to Boost.Build or superproject?

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[release] Boost 1.70.0
by Marshall Clow 12 Apr '19

12 Apr '19

Release 1.70.0 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 numerous enhancements and bug fixes for existing libraries. For details, including download links, see < http://www.boost.org/users/news/version_1.70.0> You can also download directly from: < https://dl.bintray.com/boostorg/release/1.70.0/source> SHA-256 sums: ae2bb1b35d1f238e72e3f819b42336f4bd27c9ed2092aab5d87818ccb0c9161a boost_1_70_0.7z 430ae8354789de4fd19ee52f3b1f739e1fba576f0aded0897c3c2bc00fb38778 boost_1_70_0.tar.bz2 882b48708d211a5f48e60b0124cf5863c1534cd544ecd0664bb534a4b5d506e9 boost_1_70_0.tar.gz 48f379b2e90dd1084429aae87d6bdbde9670139fa7569ee856c8c86dd366039d boost_1_70_0.zip To install this release on your system, see < http://www.boost.org/doc/libs/release/more/getting_started/index.html> Thanks to everyone who participated in this release. Thanks, -- The Boost Release Team Vladimir Prus, Marshall Clow, Daniel James, Micheal Caisse

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[release] 1.71.0 open for merging
by Marshall Clow 12 Apr '19

12 Apr '19

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

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[variant2] Gavin's review
by Gavin Lambert 12 Apr '19

12 Apr '19

This is my review of Variant2. I vote to ACCEPT this library. However I find the ambiguous state of "expected" a bit too ambiguous (and the "expected" concept in general has caused quite a bit of discussion and contention in the past) so I would prefer that it not be considered part of the library as is, and go through at least a mini-review before entering Boost. I'm not suggesting that this be a formal acceptance condition, however. (I did not look at this type for my review.) I also question whether a more descriptive name than "Variant2" can be used for it, although I recognise that at least starting the library name with "variant" is a good idea to aid discoverability in alphabetic sorting order. - What is your evaluation of the design? As I've stated elsewhere, I feel that if you're willing to pay the cost of double-buffering then you might as well go all-in and implement the strong guarantee as well (or at least a partially strong guarantee, where any attempt to change the stored type provides the full strong guarantee but attempts to assign the same type merely delegates to the underlying type's assignment operation and so provides the same guarantee as that -- this seems sufficiently reasonable and useful to me without sacrificing too much performance, and still lets you single-buffer as an optimisation when all types are noexcept assignable). Having said that, I recognise that others have different lines in the sand, and this is a reasonable design choice within those lines. - What is your evaluation of the implementation? Overall, good. I do have a few minor nitpicks: 1. bad_variant_access's constructor should be "constexpr = default" to preserve constexpr and/or triviality (if std::exception is also constexpr and/or trivially constructible, although this is not the case in VS2017, but could be in other implementations). 2. When std::monostate exists, it should treat both equivalently, for compatibility. (It should not alias its own to std::monostate, as that poses ABI problems if not all code is compiled in C++17 mode.) 3. The duplicated include guard around <boost/mp11.hpp> seems both ugly and unnecessary. Also it should probably be included after <boost/config.hpp>. 4. It's not clear why some of the internal methods (such as _get_impl) have leading underscores while others (such as emplace_impl) do not. It seems inconsistent. 5. It's not clear what purpose the "none" storage type serves (other than apparently requiring the indexing to be offset by one). It seems rather like an empty state... (and the continual offsetting seems inefficient; most of it happens at compile time, but not all). 6. variant_base_impl::_replace has a "requires" comment; why doesn't it have a matching assert? Also, why are these not BOOST_ASSERTs? 7. As discussed elsewhere, a public trait should be provided which lets you static_assert which implementation was actually instantiated. - What is your evaluation of the documentation? It is minimal but sufficient for readers already familiar with std::variant. (And who can read standardese.) It is not sufficient for readers not familiar with std::variant. I think this is mostly fine, but I would prefer the addition of a Motivation and/or Design Rationale section which explains why this is better than std::variant and boost::variant. In future it would also be nice to have a Porting section which explains what code changes are required to move from those to this. - What is your evaluation of the potential usefulness of the library? It seems potentially useful for others, although I would personally have preferred different design choices. - Did you try to use the library? With which compiler(s)? Did you have any problems? I did not try it. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I read through the documentation and code in moderate detail, but not in-depth. - Are you knowledgeable about the problem domain? I am familiar with variants, but have not as yet used them much in production code.

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Variant2 review
by Phil Endecott 11 Apr '19

11 Apr '19

Dear All, Here is my brief review of Peter Dimov's proposed Boost.Variant2. Sorry that this is not a particularly thorough review. I have read the docs, scanned the code, and followed the discussion on the mailing list; I have not tried to compile or use it. I have recently been using the original Boost.Variant for the first time. I actually started writing code based on std::variant, but then realised that I don't have support for it on one C++14-only platform, so changed to Boost.Variant. It's unfortunate that Boost.Variant has a somewhat different interface from std::variant, so it would be useful to have a Boost variant that is (more) compatible with std::variant. It would also be useful if it were somewhat backward compatible with the old Boost.Variant. The proposed Boost.Variant2 is compatible with std::variant; could some thin layer of compatibility be added to make it possible to port from Boost.Variant code? Specifically, the differences I have noticed are apply_visitor vs. visit and get(V*) vs. get_if. In my case, my stored types are typically raw pointers or small POD structs; none of these can throw during construction/assignment so the complicated arguments about exception guarantees are not applicable. Personally for my current application I'd be happy with a simpler variant that requires noexcept types, or disables assignment for types that might throw, or just doesn't offer an exception safety guarantee. Ideally, perhaps a Boost.Variants *library* should provide a selection of different variants with different features? That leads to the question of naming; we have boost::variant, boost::variant2 and std::variant and those names tell us nothing about how they differ. I'm unsure how or if this can be improved; I'm not suggesting that variant2 should be renamed variant_never_empty_maybe_double_size! But maybe the long-name of the library, i.e. what people will see when they look at the list of Boost libraries, could say "Never empty variant" rather than "Variant 2"? Prior to the review I was familiar with the issue of dynamic allocation, the fact that is is needed in some cases by some variant implementations, and the desire to avoid it. However I was not aware of the alternative of storing two copies of the union, doubling the size of the variant. Much of my work is with memory-constrained systems and unknowingly using twice as much memory as expected would be very undesirable. (I noticed Niall Douglas' comment earlier today "There is nothing wrong, *whatsoever*, with a variant which is sized the largest of its possible states multiplied by two" - I strongly disagree with that.) I'd like to at least get a warning if that were going to happen. A specific concern is that I might accidentally get this fallback due to forgetting to write "noexcept" somewhere (e.g. when using types from older code). On the subject of size, I note that the index is stored in an int, while virtually all uses would surely need fewer than 256 (or certainly 2^16) alternatives. Of course changing the index to uint16_t would not actually help on many platforms due to structure alignment requirements. This makes me wonder about a specialised variant for pointers that uses the spare bits in (most/some) 64-bit pointers to store the variant index. This could usefully be part of a variants *library*. I read Andrzej Krzemienski's comments about the documentation and largely agree with them - though I would say that this library is close enough to std::variant that perhaps the right thing to do is simply to say "go and read about std::variant and then come back here to see the differences". Peter posted a link to some benchmark results last week; those numbers are encouraging and it is also good to know that Peter actually made the effort to measure them! I do wonder how a "trivial" variant supporting only noexcept types would compare, though. Boost.Variant has something called polymorphic_get. I am unclear whether Boost.Variant2 (and/or std::variant) somehow support this functionality. The situation re. expected is unfortunate. I believe really the review should have waited for it to be completed. Peter's comment that if it is decided that it needs to be reviewed then he would remove it and never resubmit it was ... surprisingly undiplomatic? I have always found it a bit odd that Boost requires a thorough review of an initial library submission but nothing at all for later additions. In summary: - I believe the library should be accepted. - It would be great if some compatibility features with Boost.Variant could be added, to make it possible for users of that older library to transition more easily. That is not a condition for acceptance. - I would love to have some way to get a warning or error if the double storage mode had been triggered, or to disable that mode (with an error). - It would be great to see some alternative variants, with different features / trade-offs, included in the library. Ideally, naming of types and headers should allow for that. I'm not suggesting that Peter should be personally expected to supply these alternatives, but perhaps he would accept offerings from others. - I think we should allow Peter to "slip in" his expected when it is ready; I say this largely because Peter has a long history with Boost. Future review managers should try to avoid situations like this arising. Regards, Phil.

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[release] Boost 1.70.0 Release Candidate 2 available
by Marshall Clow 11 Apr '19

11 Apr '19

The second release candidate for the 1.70.0 release are now available at: <https://dl.bintray.com/boostorg/release/1.70.0/source/> Changes since rc1: * Boost.Config changes to work better with msvc-14.2 * Boost.Beast bug fixes * Boost.Move bug fix * Boost.Math non-ascii characters removed from header file The SHA256 checksums are as follows: 882b48708d211a5f48e60b0124cf5863c1534cd544ecd0664bb534a4b5d506e9 ./boost_1_70_0_rc2.tar.gz 430ae8354789de4fd19ee52f3b1f739e1fba576f0aded0897c3c2bc00fb38778 ./boost_1_70_0_rc2.tar.bz2 48f379b2e90dd1084429aae87d6bdbde9670139fa7569ee856c8c86dd366039d ./boost_1_70_0_rc2.zip ae2bb1b35d1f238e72e3f819b42336f4bd27c9ed2092aab5d87818ccb0c9161a ./boost_1_70_0_rc2.7z As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Boost Release Managers

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Problem with generating file_descriptor suing existing pipe file descriptor
by Russell West 10 Apr '19

10 Apr '19

Our program just installed version 69 of Boost and I am running into a compile issue that I am not sure how to resolve. Following is the associated section of C++ code that I am unable to figure out the changes to get it to compile. int filedes[2]; if ( pipe(filedes) == 0) { using namespace boost::iostreams; stream<file_descriptor> results(filedes[0], close_handle); .... .... } The last provided line of code does not compile with a no matching function for call to 'boost::iostreams::file_descriptor::file_descriptor(int&, file_descriptor_flags&)' error. I noticed in the version of the boost file_descriptor.hpp loaded and being used the following exists: #ifdef BOOST_IOSTREAMS_WINDOWS file_descriptor(int fd, file_descriptor_flags); #endif The associated application attempting to be built and deployed is only for servers running the Linux operation system so BOOST_IOSTREAMS_WINDOWS is not enabled, causing the above constructor not to be available. The other constructor available is file_descriptor(handle_type fd, file_descriptor_flags); but I can not figure out how to generate a detail::file_handle from the available int file descriptor generated from above pipe command. Will it cause any issues enabling BOOST_IOSTREAMS_WINDOWS so the required constructor will be available? Thanks ahead of time for your time and feedback. Russell West

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Re: [boost] [Boost-GIL] Image Processing Algorithms
by Mateusz Loskot 10 Apr '19

10 Apr '19

On Wed, 10 Apr 2019 at 18:54, Amir Ali <amirqadir(a)live.com> wrote: > > I really want to do this project even if I am not considered for GSOC. > I am still willing to do it on my own with guidance and supervision from any mentor. There are two mentors who will mentor three students in total. So, we can not offer any supervision to more projects. You are welcome to post your questions to the boost or boost-gil lists, or ask on Gitter room or the Slack channels as any user of / contributor to Boost libraries can do. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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[Boost-GIL] Image Processing Algorithms
by Amir Ali 10 Apr '19

10 Apr '19

Hi, I am looking for someone to mentor me for my project that is to implement image processing algorithms in Boost-GIL. Here’re some of the algorithms I am aiming to make. Mathematical Morphology (Dilation, Erosion, Opening, Closing) Filters (High pass Filters, Low Pass Filter which includes Gaussian etc) And Other Image enhancement basic algorithms. Regards Amir

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[variant2] Andrzej's review -- documentation
by Andrzej Krzemienski 10 Apr '19

10 Apr '19

Hi Everyone, This is the review of the documentation of variant2. First, the docs assume that the user is already familiar with std::variant or boost::variant, and the introductory part only highlights the difference from std::variant. It does not even mention that variant<X, Y> always stores either X or Y. "Type-safe discriminated union (variant) type," sounds arcane to novices. Notation variant<T…> is also confusing to someone who encounters variant for the first time. There is no initial example. No mention of visit() which is the most important part of the interface. Compare this with Boost.Variant docs: https://www.boost.org/doc/libs/1_69_0/doc/html/variant.html I do not think the library should assume this. Boost libraries are characteristic of documentation that introduces potential users to the problem domain and gives a sort of tutorial that shows how to use the library. I recommend doing the same for variant2. This library does a lot of contortions to avoid the valueless state, but does not describe what the motivation for it is. The docs also do not give a sense of what performance (spacial and runtime) trade offs this library does. For instance, we do not know if the double-buffer scenario th second buffer is within variant's storage or on the heap. Or we do not know about secret moves that the library does internally, which gives surprising behavior to the users that store non-movable types in variant. Consider the following example: ``` struct X {}; struct Guard { explicit Guard(int) {} Guard(Guard&&) = delete; }; variant<X, Guard> v {}; v.emplace<Guard>(1); ``` This works fine with std::variant, but fails to compile with variant2::variant, because the latter requires all the alternative types, at least in one implementaiton of the never-empty trick, to be move-constructible. But this requirement is never listed in either global requirements for alternative types stored in variant, or in the specification of functions `emplace()`. Here's a wandbox example: https://wandbox.org/permlink/hGbRtgzpUrpF0ODy The Reference part of the docs is really good and detailed. Some minor "bug reports" follow. In the specification of functions types `T0` and `Ti` are used, but `T0` or `Ti` are never defined. Wording in the C++ Standard also refers to `T0` and `Ti`, but also provides a definition: In the descriptions that follow, let i be in the range [0, sizeof...(Types)), > and Ti be the ith type in Types. > <http://eel.is/c++draft/variant.ctor#1.sentence-1> > See http://eel.is/c++draft/variant.ctor#1 A similar definition should be put in variant2's documentation. Noexcept specifications use mp_all. this assumes that users of variant2 must be familiar with Boost.mp11. I recommend removing the reference to mp_all and instead use something similar to what the Standard does: http://eel.is/c++draft/variant.ctor#11 Specification of function `emplace()`: It says: > > On exception: If the list of alternatives contains monostate, the > contained value is either unchanged, or monostate{}; > In what situation on exception is the contained value left unchanged? This question applies to the next bullet as well. The specification also doesn't mention that `.emplace()` requires Ti to be move-constructible in some cases. It also says: Throws: Nothing unless the initialization of the new contained value throws. Which sounds strange, because it does throw something. In other places you use "Throws: Any exception thrown by the initialization of the contained value.", which makes more sense. Also, the Standard uses, "Throws: Any exception thrown during the initialization of the contained value. <http://eel.is/c++draft/variant.mod#11.sentence-1>": http://eel.is/c++draft/variant.mod#11 swap(): What does it throw and when? Other functions specify it but this one does not. get(): Specification says, > > If v.index() is I, returns a reference to the object stored in the > variant. Otherwise, throws bad_variant_access. > This means that if I provide an index that is far greater than `sizeof...(T)`, the program should compile fine and throw an exception at run-time. This is not what the implementation does: I get a compile-time error, which is good, but inconsistent with the docs. They need an additional "Requires:" clause. visit(): I think it is underspecified. It is not immediately clear that the first parameter is the visitor and the remaining ones are variants. Parameter names F and V do not convey this clearly. Either use Visitor and Variants... or provide a longer description, even if informal. The docs really should contain an example of `visit()` somewhere. According to the specs, the following should work: ``` void f() {} variant2::visit(f); ``` which is not incorrect, but strange. The std::variant also provides a second overload of `visit` that explicitly defines the return type: http://eel.is/c++draft/variant.visit This overload is not present in variant2. But this fact is not listed in the initial section of the docs that lists the differences between the two libraries. Regards, &rzej;

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[variant2] Comments on documentation
by Bjorn Reese 10 Apr '19

10 Apr '19

The overview states that "variant<T...> is not trivial when all contained types are trivial". Why not? Is this an advantage somehow or an unfortunate limitation? Why is there no tutorial? Why is there no design rationale? Change "variant_npos = -1" into "variant_npos = unspecified" Add a comment about the purpose of valuesless_by_exception(). Without such a comment, the function seems very odd on a "never valueless variant type." The destructor should be marked as noexcept.

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[variant2] Review - Review period extended until April 15
by Michael Caisse 09 Apr '19

09 Apr '19

Hi all - The review period for Boost.Variant2 has bee extended to April 15. Thank you to those who have participated so far. There has been a fair amount of discussion about the merits of never valueless. A core design _feature_ of Variant2 is never valueless. You may have made different trade-offs. Understanding motives makes sense but in this review we are not trying to change this basic design choice. This paper by Peter discusses valueless variants some and may be useful reading: <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0308r0.html> If you haven't started your review yet, you have time! Reviews ranging from detailed discussions of inner workings to a user-perspective of the library and documentation are all helpful. I personally believe we need more user-based reviews in Boost. So, feeling sheepish about reviewing? Don't! Your review is important in the process. Here is one more motivation if you are on the fence ... Peter's code is a joy to read. The library is extremely clean and the code is accessible. There might be all kinds of things you learn from reading the source. Thank you again community for staying involved. We get great libraries when people ask questions, review, and provide input to everything from the docs to the design. Happy coding! michael -- Michael Caisse Ciere Consulting ciere.com

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GSOC 2019 proposal
by Siddhartha Sen 09 Apr '19

09 Apr '19

Once the proposal is ready, where do I officially submit the pdf?

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Re: [boost] [release] Boost 1.70.0 Release Candidate 1 available
by Ion Gaztañaga 09 Apr '19

09 Apr '19

On 07/04/2019 15:07, Rainer Deyke via Boost-users wrote: > On 07.04.19 14:13, Marshall Clow via Boost-users wrote: >> On Sat, Apr 6, 2019 at 10:53 AM Rainer Deyke via Boost-users < >> boost-users(a)lists.boost.org> wrote: >> >>> On 04.04.19 16:27, Marshall Clow via Boost-users wrote: >>>> 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. >>> >>> boost::movelib::adaptive_merge continues to be broken if >>> iterator_traits<RandIt>::size_type != std::size_t. This breaks >>> boost::container::flat_map when cross-compiling for MacOS. I have >>> previously reported this error here. >>> >>> I consider this a critical error - as in, I won't be able to upgrade to >>> Boost 1.70 at all unless this error is fixed for the release. >>> >> >> This is https://github.com/boostorg/move/issues/25, correct? > > Yes. Sorry for note replying earlier, I was on a trip. The fix is not complicated but several files need to be modified. Committed to develop: https://github.com/boostorg/move/commit/bfdfca0b88fe1cf4e67b42fcacd5e126e93… @Rainer: I've checked this fix in several msvc and gcc's locally. The error report does not contain any example for the bug, so I don't know if I've fixed your use case. I don't know if we are still on time for 1.70. Best, Ion

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[variant2] request to extend the review period
by Andrzej Krzemienski 08 Apr '19

08 Apr '19

Michael, Peter, Would it be possible to extend the review period? I may only be able to devote more time to the review on Thursday, so if it was possible to extend the review at least till 12th, I might have a chance to get it done. I suspect, I might be not the only one in this situation. Regards, &rzej;

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Re: [boost] variant - off topic
by Bjorn Reese 08 Apr '19

08 Apr '19

On 4/3/19 11:27 PM, Robert Ramey via Boost wrote: > d) insert your own use case here. That is, look at your own usages of > assignment to these types and see if there is not an easy way to > re-factor your code to avoid assignment. Such refactoring is difficult for state machines where you use a variant to denote the current state.

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Enabling spectre mitigation in boost libraries
by Riff J 08 Apr '19

08 Apr '19

Hi everyone, I am a developer from Microsoft and currently using boost in our project. We recently get noticed by our security team, that the boost library we use, are not compiled with spectre mitigation (/Qspectre) enabled. Since boost is super powerful, it might not be a good idea to write our own or maintain our own version, so we are reaching out for help. Could anyone please help see if we could enable /Qspectre option in the official build of boost? And here is the vcblog about the spectre mitigation, if anyone is interested: https://blogs.msdn.microsoft.com/vcblog/2018/01/15/spectre-mitigations-in-m… . And since this is the first time I use this mail list, please let me know, if I didn't use it correctly or anything I should pay attention to. Thanks a lot, Riff

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[gsoc19] Boost.Geometry Delaunay triangulation and Voronoi diagrams
by Georgios Venizelos 08 Apr '19

08 Apr '19

Hello, I would like to undertake the Delaunay/Voronoi project in Boost.Geometry library. I have already shared my proposal on GSoC through Google Docs. I think that Delaunay triangulation is a process that has many applications, so it is useful to have such a process implemented in Boost libraries. Main focus of the program would be to implement Delaunay and Voronoi for Cartesian coordinates in 2 and 3 dimensions. If finished early, this could extend either in higher dimensions or in other coordinate types. Would anyone be interested in mentoring such a GSoC project? With respect, Georgios Venizelos --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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Re: [boost] Enabling spectre mitigation in boost libraries
by Kenneth Porter 08 Apr '19

08 Apr '19

On 4/6/2019 9:46 AM, John Maddock via Boost wrote: > One thing we could look at for future releases would be to provide > differently-named binaries for /Qspectre. Anyone else have thoughts > on that? I just looked at the libraries available via the Visual Studio installer and I see this in my installation (using atls as an example MS-supplied library): C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.20.27508\atlmfc\lib\spectre\x64\atls.lib C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.20.27508\atlmfc\lib\spectre\x86\atls.lib C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.20.27508\atlmfc\lib\x64\atls.lib C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.20.27508\atlmfc\lib\x86\atls.lib That may give some guidance as to how MS can package the Boost libraries for internal distribution.

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Re: [boost] [variant2] Andrzej's review -- design
by Mike 08 Apr '19

08 Apr '19

> Going back to variant, in one case, we are defining an empty state, which > forces the user to provide explicit handling for that state, *everywhere*. You keep repeating that the user would have to explicitly handle that everywhere. I thought I just showed you that this is not the case. Except for visit, you don't have to explicitly handle the valueless state at all and even in the case of visit, you might be fine with std::visit just throwing an exception, because that is indeed an exceptional circumstance. I don't see this *everywhere* at all. Best Mike

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[release] Master branch now completely closed for the 1.70.0 release
by Marshall Clow 08 Apr '19

08 Apr '19

The master branch is now closed for all changes except by permission for the release. Also, remember to add your libraries' changes to the release notes at: < https://github.com/boostorg/website/blob/master/feed/history/boost_1_70_0.q… > Thanks, -- The Boost Release Team

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Regarding Boost.Astronomy GSoC19 proposal review
by sarthak2007 07 Apr '19

07 Apr '19

Hello community, I am Sarthak Singhal, pursuing B.Tech in Computer Science from Indian Institute of Technology, Kanpur. I had submitted the programming competency test to mentor and also got a positive response from her. I had also submitted the project proposal to the mentor and based on her suggestions have improved it also. I have submitted the draft of the proposal to GSoC site. I request you to go through the proposal. I will appreciate your feedback to improve the proposal. Thank you, Sarthak Singhal -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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[release] Boost 1.70.0 Release Candidate 1 available
by Marshall Clow 07 Apr '19

07 Apr '19

The release candidates for the 1.70.0 release are now available at: <https://dl.bintray.com/boostorg/release/1.70.0/source/> The SHA256 checksums are as follows: 6e5cba1269225395bb5e78dda48441ccadaf745e42638180015e9e6257068336 ./boost_1_70_0_rc1.7z 35d8e1361e2063f70aa3a6ca0dd8af0877ceb75477ebbd2c726bb1d039658c7a ./boost_1_70_0_rc1.tar.bz2 ec8ddbbee2fd61e2f78a1dfe9a07ad83ca8f6a2f4c704d6f297d89c6afdc4f2c ./boost_1_70_0_rc1.tar.gz ee2c3b97ce10f85a31b6a105ad8edf1c20fb4b936c9a6e6008206059cb98ab1b ./boost_1_70_0_rc1.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Boost Release Managers

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Re: [boost] [Boost-users] [release] Boost 1.70.0 Release Candidate 1 available
by Marshall Clow 07 Apr '19

07 Apr '19

On Sat, Apr 6, 2019 at 10:53 AM Rainer Deyke via Boost-users < boost-users(a)lists.boost.org> wrote: > On 04.04.19 16:27, Marshall Clow via Boost-users wrote: > > 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. > > boost::movelib::adaptive_merge continues to be broken if > iterator_traits<RandIt>::size_type != std::size_t. This breaks > boost::container::flat_map when cross-compiling for MacOS. I have > previously reported this error here. > > I consider this a critical error - as in, I won't be able to upgrade to > Boost 1.70 at all unless this error is fixed for the release. > This is https://github.com/boostorg/move/issues/25, correct? -- Marshall

1 0

[gsoc 19] Review of the proposal draft
by pranay gupta 07 Apr '19

07 Apr '19

Hi list, I have submitted the first draft of my proposal for implementing non-negative matrix factorisation in boost.ublas. It would be really helpful if you could please review it and suggest any improvements. Thanking you in advance. Sincerely, Pranay

2 3

Variant2 review
by Niall Douglas 07 Apr '19

07 Apr '19

I'll firstly apologise for the brevity of this review. It is just before the ACCU conference where I am speaking on a topic I have little knowledge of, and I have done almost no prep due to insufficient hours in the day. I am aware that if I don't make a review now, then I won't at all, so this will have to do. 1. Overall I like the library, it adds significant benefit (primarily removal of dynamic memory allocation) over Boost.Variant. 2. I don't like the lack of propagation of triviality of each individual special member functions. std::variant does this. std::expected does this. I can see Peter's point that for long lists of alternative states, implementing this is a lot of pain for almost no gain. However I do NOT agree with him for Expected. For a two-state variant, it is very highly likely that triviality of special member function will be very important for not a small number of use cases. I personally am happy for Variant2 to implement Expected without review approval here IF that Expected matches exactly std::expected. I am NOT happy if Variant2's Expected breaks conformance on triviality of special member function. If that is the only option on the table, then either please do not include an Expected implementation, or don't include Variant2. This raises a wider point though. What is good for a two-state variant still applies, though less so, to three-state variants, four-state variants and so on. I think there is a fundamental design issue here. If Variant2 can't propagate triviality of individual special member functions for small-number-of-state variants, then there is something fundamentally wrong here. 3. I find the design choice to randomly permute state to avoid an empty state baffling when there is a double buffer based design choice available. I do not like, one bit, the random permutation of state. I think it will lead to buggy code with hard-to-test corner cases. I think it needs to go away in the proposed design. I also don't get the dislike of the double buffer based design. Peter seems to really dislike it, and avoids it whenever possible. I can't understand why. If you can employ a double buffer design in order to eliminate random permutation of state, to me this is an unalloyed good in every way. Nowhere does it say that a variant must be no larger than the largest of its possible states. There is nothing wrong, *whatsoever*, with a variant which is sized the largest of its possible states multiplied by two. So please change the design to that instead. That should be the default design, and design claims. Programmers should write code assuming that design. IF it can be proven that a double buffer is unnecessary e.g. all alternative types are noexcept, a monostate alternative is available etc, THEN you can employ a single buffer implementation as an *optimisation*. That makes thing simple for the end user: add monostate, get single buffer sized. Otherwise assume double buffer sized. With a default double buffer design, most of the other issues which other reviewers have raised go away. Even Robert's concerns about assignment operators, with a double-buffer-by-default design one can always implement the strong guarantee. I badly need to depart, so I'll have to end there by saying that I vote to ACCEPT, conditional on (i) propagation of triviality of special member functions for at least small numbers of alternative states and (ii) removal of ANY POSSIBILITY of random permutation of chosen state under ANY circumstances. Finally, thanks Peter for bringing this library for review. Nice library. Niall

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Proposal for GSoC'19 ( Random Points Generation)
by Mudit Agarwal 06 Apr '19

06 Apr '19

Hi I am submitting my first draft of the proposal for the project, Implementing algorithm for random point generation according to some given distribution in a geometry. I have also implemented competency test for the project https://github.com/Mudit-1999/Random_Points_Generation. It would be really helpful if you could please check if I have fulfilled all the points mentioned to pass competency test. Can you also please review my proposal and suggest any improvement. Hereby attach is my proposal. Thanking you in advance Regards, Mudit Agarwal

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[review][variant2] Variant2 Review Starts April 1
by Michael Caisse 06 Apr '19

06 Apr '19

The Boost formal review of Peter Dimov's Variant2 library will take place April 1 - 10, 2019. Please consider participating in this review. The success of Boost is partially a result of the quality review process which is conducted by the community. You are part of the Boost community. I will be grateful to receive a review based on whatever level of effort or time you can devote. Variant2 is a never-valueless C++11/14/17 implementation of std::variant. >From the README: The class boost::variant2::variant<T...> is an almost conforming implementation of std::variant with the following differences: * A converting constructor from, e.g. variant<int, float> to variant<float, double, int> is provided as an extension; * The reverse operation, going from variant<float, double, int> to variant<int, float> is provided as the member function subset<U...>. (This operation can throw if the current state of the variant cannot be represented.) * variant<T...> is not trivial when all contained types are trivial. To avoid going into a valueless-by-exception state, this implementation falls back to using double storage unless * one of the alternatives is the type monostate, * one of the alternatives has a nonthrowing default constructor, or * all the contained types are nothrow move constructible. If the first two bullets don't hold, but the third does, the variant uses single storage, but emplace constructs a temporary and moves it into place if the construction of the object can throw. In case this is undesirable, one can force emplace into always constructing in- place by adding monostate as one of the alternatives. You can find the source code here: <https://github.com/pdimov/variant2> and the documentation here: <https://pdimov.github.io/variant2/doc/html/variant2.html> Please take an early look at the library and ask questions now. Peter Dimov is very active on the Cpplang Slack #boost channel; however, please consider using the Boost Dev or User Mail Lists so that the entire community might benefit from your conversation. Note: The repository contains an expected implementation also; however, that is not being considered in this review. Thank you for your participation! michael -- Michael Caisse Ciere Consulting ciere.com

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[gsoc19] looking for mentor
by Aziz Mousa 06 Apr '19

06 Apr '19

hi, I have my idea to contribute in boost project, I read the boost libraries list and see that the author of Algorithm is "Marshall Clow" I want to know how to contact with him to tell him about my idea. thanks.

1 0

Call for Speakers: International Conference on Information Society (i-Society 2019)
by International Conference on Information Society 06 Apr '19

06 Apr '19

If you are not able to see this mail, click http://r.confinfosoc.org/mk/mr/qLUGBQMxp4Sjs2NE4YExi3z5lvlWCZKGhXcL8vLsIM2b… for Speakers: International Conference on Information Society (i-Society 2019) [ ]( http://r.confinfosoc.org/mk/cl/f/SUXNTtBZKKIQS3K7XMAgqz2d4gwN08R7QeY-JpBOAY… ) Submission i-Society 2019 Call for Speakers is an open invitation. We sincerely hope that you could give a talk to the diversity of participants. Increase numbers of renowned speakers have confirmed their participation. If you are interested in giving a talk, please complete the form at http://r.confinfosoc.org/mk/cl/f/WcSYgytshsQLNmvIxy3wVH45pNQcePlyBDtX1_3wdq… before or by the 1st of May, 2019. [ Submission ]( http://r.confinfosoc.org/mk/cl/f/-hT6brTC-Gpj8JwZIfXWMoq1tq9fO0kmb4uz_A4rSS… ) This email was sent to boost(a)lists.boost.org You received this email because you are registered with Infonomics Society [ Unsubscribe here ]( http://r.confinfosoc.org/mk/un/IcFogLSqu5RwSkorQ9Mu-bTdNLGBdU-QcdZpGWjlqfqJ… ) Sent by [ ]( http://r.confinfosoc.org/mk/cl/f/3aG3a0Qf4pxEQF2aHlpkSK0PjUVKbrOE2FXQYnchXN… ) © 2019 Infonomics Society

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auto_link.hpp update for Visual Studio 2019 GA release
by Trueman, Chris 06 Apr '19

06 Apr '19

Building boost with the GA release of Visual Studio 2019 names the outputs with v142 (which matches what VS 2019 names its build tools). But auto_link.hpp causes the linker to look for files named with v141. I changed auto_link.hpp to: # elif defined(BOOST_MSVC) && (BOOST_MSVC < 1910) // vc14: # define BOOST_LIB_TOOLSET "vc140" # elif defined(BOOST_MSVC) && (BOOST_MSVC < 1920) // vc14.1: # define BOOST_LIB_TOOLSET "vc141" # elif defined(BOOST_MSVC) // vc14.2: # define BOOST_LIB_TOOLSET "vc142" This corrected the linker errors on my machine. I'm happy to submit this properly but thought I'd check it with folks here first. Chris. INTELLICORP LEGAL NOTICE: This E-Mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying or other use of this message or its attachments is strictly prohibited. If you received this message in error, please notify the sender immediately by replying to this message, and then delete it.

1 1

GSoC'19 [Boost.Geometry : Implementing algorithms for the concave hull problem]
by yaghyavardhan singh khangarot 06 Apr '19

06 Apr '19

Hi, I am interested in contributing to Boost.Geometry and would like to work on the Project 1 (Implementing algorithms for the concave hull problem) as my GsoC’19 project. I had some discussion regarding this with Adam Wulkiewicz. I have read the paper ( Moreira, Adriano J. C., and Maribel Yasmina Santos. “Concave hull: A k-nearest neighbors approach for the computation of the region occupied by a set of points.”) and currently going through the paper “A New Concave Hull Algorithm and Concaveness Measure for n-dimensional Datasets*” ( https://www.iis.sinica.edu.tw/page/jise/2012/201205_10.pdf )) . These are the papers given in the project description. I am also searching for any other algorithms (newer or better) for the concave hull problem. Please direct me to any other algorithms related to this project. Regards Yaghyavardhan

2 3

[GSOD19] Mentors registration
by Damian Vicino 06 Apr '19

06 Apr '19

Hi, I started the registration process for Google Season of Docs, please contact me if you want to mentor to do the formalities. Each documentor requires 2 mentors in GSOD, so the work will be collaborative. Best regards, Damian Vicino

2 2

Re: [boost] [Boost-users] [release] Boost 1.70.0 Release Candidate 1 available
by Tom Kent 04 Apr '19

04 Apr '19

On Thu, Apr 4, 2019 at 9:27 AM Marshall Clow via Boost-users < boost-users(a)lists.boost.org> wrote: > The release candidates for the 1.70.0 release are now available at: > <https://dl.bintray.com/boostorg/release/1.70.0/source/> > > The SHA256 checksums are as follows: > 6e5cba1269225395bb5e78dda48441ccadaf745e42638180015e9e6257068336 > ./boost_1_70_0_rc1.7z > 35d8e1361e2063f70aa3a6ca0dd8af0877ceb75477ebbd2c726bb1d039658c7a > ./boost_1_70_0_rc1.tar.bz2 > ec8ddbbee2fd61e2f78a1dfe9a07ad83ca8f6a2f4c704d6f297d89c6afdc4f2c > ./boost_1_70_0_rc1.tar.gz > ee2c3b97ce10f85a31b6a105ad8edf1c20fb4b936c9a6e6008206059cb98ab1b > ./boost_1_70_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. > Windows/Visual Studio (msvc 10.0, 11.0, 12.0, 14.0, 14.1) builds look good. toolset arch compile Link Execute msvc-10.0 32 X X X msvc-10.0 64 X X X msvc-11.0 32 X X X msvc-11.0 64 X X X msvc-12.0 32 X X X msvc-12.0 64 X X X msvc-14.0 32 X X X msvc-14.0 64 X X X msvc-14.1 32 X X X msvc-14.1 64 X X X Compile means that the b2 command completed without errors Link means that visual studio was able to link a sample executable to a library (libboost_thread-vcXXX-mt[-gd]-1_XX.lib) generated Execute means that the linked program executed without errors. Full build logs can be found at: https://gist.github.com/teeks99/798df332c12ec98708e3710da35dd606 Tom

2 1

[variant2] Andrzej's review -- design
by Andrzej Krzemienski 04 Apr '19

04 Apr '19

Hi Everyone, First of all, I wanted to thank Peter for writing this non-trivial library and sharing it with the community. This is not a full review yet. I just wanted to discuss the design first, especially the never-empty guarantee. And I am going to rehash the old argument. The core of variant2 is its never-empty guarantee and the mechanism to achieve it: a number of different algorithms chosen depending on what the potentially stored types permit. In fact this mechanism is not much different than the one present in boost::variant. The issue to solve is what happens in copy/move assignment of variant<X, Y> when we have to change the stored type from X to Y. X has to be destroyed and Y initialized. But if the initialization of Y throws we would be left without either X (already destroyed) or Y (not successfully constructed). (The same problem applies to member function emplace()). Except for the last step boost::variant and variant2 try to apply the same sequence: 1. If all the subtypes have noexcept initialization, no safety measures need to be taken. 2. If sub-types have noexcept move constructor, a temporary local storage is used and the backup value is moved to and from it. 3. If one of the subtypes is a special type boost::blank or std::monostate respectively, in case of a throw this type is default constructed in the variant. 4. If there is any nothrow-default-constructible subtype in the variant, it gets default-constructed upon exception. If neither of the above can be applied, the two libraries apply different approaches. variant2 is big enough to fit two unions of X and Y within its storage. This way it does not have to destroy the X when initializing the Y. boost::variant, for the additional storage uses heap allocated memory. Interestingly, the double storage as in variant2 has been considered in the initial design of boost::variant but rejected by the community, because it added spacial overhead even for use cases that never invoked variant's assignment. This is described in the Rationale section of boost::variant documentation: https://www.boost.org/doc/libs/1_69_0/doc/html/variant/design.html#variant.… In boost.variant, only these programs pay for the overhead that really invoke the assignment operator. Neither of the solutions seems strictly superior than the other. The double storage could be thought as better because it seems to be able to cover use cases where heap allocations are banned altogether. On the other hand, in these applications it is difficult to imagine that X and Y would be throwing exceptions in move constructors or during initialization. One inferiority of boost::variant is that it can fail for its own reasons unrelated to failures of X and Y. Even if no operations on X and Y throw during the assignment of variant, the variant can still throw because it allocates memory. Some people believe that an application cannot recover from bad_alloc anyway, but this is not a universally held view. To me, the important question is, do we really need the never-empty guarantee. It was an unquestionable requirement for the initial design of boost::variant. Now, variant2 is advertised as an allegedly superior solution to std::variant, because the latter does not provide the never-empty guarantee, even though the cost of providing it is significant. But I myself fail to see the *practical* value of the never-empty guarantee. The argument I hear is that, we want to make it an invariant that either X or Y is stored in variant. I agree with this goal in general, but the costs and contortions required to satisfy it outweigh the benefit. Now, I hear that if the invariant is weakened everyone will have to check everywhere if any variant is in a valueless_by_exception state. This seems to be confirmed by the semantics of std::variant::visit(), which requires that valueless_by_exception is checked and an exception thrown on valueless. This last part is indeed strange in std::variant, but I do not agree that the fix is to provide a never-empty guarantee at the cost of compromising run-time performance and complicating the design. I can think of the following alternative design. The invariant of a variant (pun intended) allows for a valueless_by_exception state. There is no way to get to this state other than by throwing form the initialization of Y in variant's assignment or .emplace() operation. Calling .visit() on a valueless variant is UB. The destructor and reset functions such as assignment and .emplace() can handle the valueless state. This is almost what std::variant does except for UB in .visit(). Why I find this superior to variant2. 1. It is simpler, faster and smaller. 2. Observing the valueless state can only happen when somebody is handling exceptions incorrectly. And in that case this is exception handling strategy that needs to be fixed: not the variant's guarantees. It should be noted that variant2 DOES NOT PROVIDE A STRONG EXCEPTION SAFETY GUARANTEE. The never-empty guarantee has a certain negative effect of confusing people so that they are led to believe that they have strong exception safety. But they don't. even expert programmers in this forum expressed their surprise that changing from X to Y in variant<X, Y, Z> can get them a variant storing Z. Sometimes it is even trickier: X may be a container that currently stores 10 elements. You assign Y, and after the exception you get an X that stores zero elements. Because of these problems, the only reasonable thing to do is to follow the advice from Dave Abraham's article: https://www.boost.org/community/exception_safety.html To quote the relevant part, "If a component has many valid states, after an exception we have no idea what state the component is in; only that the state is valid. The options for recovery in this case are limited: either destruction or resetting the component to some known state before further use." If this principle is followed no-one will ever observe the valueless_by_exception state. This also applies to variant2. If this principle from Dave Abrahams is followed, no-one will ever benefit from the never-empty guarantee (but people will still pay the costs of providing it). You cannot do anything meaningful with variant that threw other than destroy or reset it. (But it is probably best to destroy it.) If objects are allowed to survive the stack unwinding, they should either offer a strong exception safety guarantee, or you have to have some very detailed knowledge of a given particular type how its state gets modified under exceptions, but this is usually very difficult and best left to experts. I have started a thread in this list a while ago, requesting for an example of code that *correctly handles exceptions* (does not stop stack unwinding at random places), where the programmer would make use of the never-empty guarantee , and chose something else than destroying or resetting the variant. And although I received some generic statements, referring to the purity of the design, strength of the invariants, and the easiness of thinking or "correctness", none of the proponents of the never-empty guarantee gave such an example. Which might be an indication that the problem we are solving may be nonexistent. I am not sure of this claim, but I have not seen any convincing example either. I believe that we are facing one of this problems where the strong invariants of the type need to be weakened due to practical considerations. I can see no correctness issues with valueless state other than in programs that are already exception-unsafe. Also, I have heard claims that if someone is fine with valueless state they should put std::monostate as one of the types and the same effect without double buffering is achieved. But this is not true. Variant with monostate can get the degenerate state in a correct program; often: in the variant constructor. Now I really have to special-case it whenever I inspect the variant object, which is a nightmare: this is really a weak invariant in an allegedly strong-invariant variant. In contrast, for std::variant you only get the valueless state in the program that incorrectly handles exceptions: no need to special-case the valueless_state when doing visitation.. variant2 is not a replacement for std::variant, as the choice to support never-empty guarantee at the cost of more expensive operations and increased object size is not necessarily superior. Even if my view is not generally held, it has to be acknowledged that the issue is controversial. Variant2 cannot replace boost::variant either. This is not only about supporting pre c++11, but also for different trade-offs in never-empty guarantee, which were deemed inferior in boost::variant design. variant2 is ismply a third point in the multi-dimensional design space of different trade offs for variant-like libraries. On a different subject, one thing that is missing from both: boost::variant, and std::variant, is the narrow-contract observers for the specific stored type, useful when I know by other means what is currently stored in the variant object. This is something the third variant implementation has a chance to change, however it chose to follow its predecessors. This seems somewhat counter to the spirit of C++. We requested a similar thing of Niall's Outcome library, and the narrow-contract observers were added. Below is the comparison between boost::variant, std::variant and variant2. I do not know how to make a table in the email discussion interface, so I will have to make it with a list. 1. Works in pre-c++11 dialects * boost::variant: yes * std::variant: no * variant2: no 2. Size of variant<X, Y> (when X and Y are unfriendly) * boost::variant: sizeof(void*) + SXY (SXY is the size of union{X x; Y y;}) * boost::variant: sizeof(int) + SXY * variant2::variant: sizeof(int) + 2 * SXY 3. Uses heap allocations * boost::variant: yes * std::variant: no * variant2: no 4. Throws its own exceptions in assignment * boost::variant: yes * std::variant: no * variant2: no 5. Fast (narrow contract) access to X alternative. * boost::variant: no * std::variant: no * variant2: no 7. Strong exception-safety guarantee * boost::variant: no * std::variant: no * variant2: no 8. Never-empty guarantee * boost::variant: yes * std::variant: no * variant2: yes 9. Throws its own exceptions in visitation * boost::variant: no * std::variant: yes * variant2: no Regards, &rzej;

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[variant2] Andrzej's review -- design
by Mike 04 Apr '19

04 Apr '19

> Every time you touch a variant object, you must consider the possibility of it being valueless.Â No I don't. It just works and I explained why. Could you please point out specifically where I made a mistake in my reasoning in the mail before where I discussed the behavior of all member functions? And again: I'm not arguing that one is better than the other. I'm saying it doesn't matter, but I'd much perfer a design that is in line with std::variant instead of having yet another slightly incompatible version of variant that doesn't offer any significant benefit (would be a different story if it would always offer the strong exception guarantee).

2 1

Regarding Boost.Astronomy GSoC19
by sarthak2007 04 Apr '19

04 Apr '19

Hello, For the competency test I had used quantity<length> of boost::units in place of double to store the values of coordinates with their units. But in project we have to deal with boost::geometry. One way it can be done is that whenever we use functions for dot product, cross product, etc. directly from boost::geometry then we just pass the values of coordinates in them instead of units. There will be no problem considering units in calculations as boost::units convert the values stored into SI units so all the calculations will be involving coordinates with SI units. But then we will have to change the way of storage of coordinates as boost::geometry can't be used to store coordinates(with units) as it does not support units. Is it the right approach or there is some nicer way to implement this? Thank you, Sarthak Singhal -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

2 1

[gsoc 19]proposal to project 1 Boost.GIL
by raghuchandra kanakamedala 04 Apr '19

04 Apr '19

Hi my proposal link: https://docs.google.com/document/d/1-BZO0VuIcebe1ZcdyxHGjOEkQL3eeaXwGtKCWyQ… .Please suggest me any changes if required. Thanking you K RaghuChandra

2 2

variant - off topic
by Robert Ramey 04 Apr '19

04 Apr '19

I've been and observer on the discussions regarding variant, expected, outcome, optional, outcome and ?? for sometime. I'm pretty amazed at the amount of controversy each and everyone of these in every forum - here, C++ committee, etc. I'm beginning to wonder this isn't telling us something. It seems natural that when making a new C++ data type, we should want to implement the assignment operator. Why - well every variable needs to be assigned to from time to time. Why is this so? Well ... Suppose we break this assumption and consider the idea that assignment doesn't make sense for every type. A variant is a "meta-type" or "sum type" which "holds" one of a set of other types. Such a variant can take on the character of any one of type types it is holding. When does it make conceptual sense for a variable to change it's type one it has been initially assigned. I've been trying to think of one and haven't been successful. Here are a few of the scenarios I've considered. a) Returning a sum type - the most common scenario for a variant. Doesn't require a assignment. Copy/move may still be required of course. b) looping through a vector of variants as in vector variant<...> v; for( variant<...> v : [](){...} fix with change to vector variant<...> v; for( variant<...> & v : [](){...} c) set according to condition variant<...> r; if(i < 0) r = v<t1>(...) else r = v<t2>(...) fix with change to variant <...> r = (i < 0) ? v<t1>(...) : v<t2>(...); d) insert your own use case here. That is, look at your own usages of assignment to these types and see if there is not an easy way to re-factor your code to avoid assignment. I'll concede that, influenced by functional programming style, with a little experimentation with F# and propaganda from the Haskell community, I've become accustomed to code in the above way. Also I've become afraid to assign anything to these types. The discussion has made me aware of a raft of unintended consequences of doing what on it's surface seems a trivial operation. I've gotten to the point that assignment to a variant type, or "changing the type" of a value at runtime is not code smell to me. Maybe all this could be just eliminated if this became the accepted position. Of course I realize that by engaging in the practice I do, the whole issue becomes irrelevant to me personally. And I can always create variant types as "const". It's not about that. It's about avoiding the creating of vocabulary types which lead to problems. So - simple proposal. Require that sum types have operator= deleted. Robert Ramey

3 5

[variant2] never-empty guarantee, again
by Andrzej Krzemienski 04 Apr '19

04 Apr '19

wt., 2 kwi 2019 o 22:59 Peter Dimov via Boost <boost(a)lists.boost.org> napisał(a): > Andrzej Krzemienski wrote: > > > Can you show a destructor like that, does a visitatoin on a variant, and > > that you wouldn't be ashamed to put in your program? > > The destructor doesn't have to do visitation. It merely needs to call a > function f1, which calls a function f2, which calls a function f3, which > calls a function f4, which does visitation. > > What we've been telling you from the start is that this forces you to > partition your functions into two classes, one allowed to do visitation, > the > other not, then keep track of which is which, never calling the wrong > class > in a destructor, or from a catch clause. > The fact that I have to partition all functions into two categories isn't new or surprising. When defining an operation that needs to provide a strong exception-safety guarantee I need to some use operations that offer no-fail guarantee. So I need to be aware which operations offer no-fail guarantee and use only those. I do the partitioning, and I need to be cautious. When I define the destructor, again I do not have the liberty to use any function I can use in other parts of the code. In destructor I can only use functions that do not signal failure through exceptions if they fail. And not signalling failures is ugly on its own, so I am inclined to also just use functions that cannot fail. I have to do the partitioning again. When I try to go back and recall how the destructors I write look like, they fall into three categories: 1. Some types just aggregate other types. The implicitly defined destructor only calls the destructors of subobjects. 2. Sometimes I need to provide a RAII interface for a system resource or a C component. In that case my implementation uses only ints and pointers and system calls. When defining the destructor, I have confidence that there are no unexpected types hidden by templates, or functions with unexpected types with unpredictable guarantees. 3. When I define a generic component, such as optional<T>, in my destructors the only operation on the unknown type T is to call its destructor. Other operations in the destructor are performed on concrete types with no-fail guarantee such as `bool`. The situation is no different for std containters: for T, they only call destructors, other operations are on concrete types: pointers, memory deallocation. No way a variant or other unexpected type could get there, even indirectly. I know people are using destructors for other things, like committing the DB transaction, but this is what I call bad exception handling. Such implementations are usually incorrect: either you do not report failures in such case, or you are reporting failures when there is none. Your example of a destructor, to me, also falls into this category: template<class T> class monitor > { > char const* file_; > int line_; > T const& v_; > T old_; > > public: > explicit monitor( char const* file, int line, T const& v ): > file_( file ), line_( line ), v_( v ), old_( v ) {} > > ~monitor() > { > if( v_ != old_ ) { > std::clog << file_ << ":" << line_ > << ": monitored value changed from " > << old_ << " to " << v_ << std::endl; > } > } > }; It calls operations on an unknown T that could fail and throw: comparison, streaming. Streams themselves could throw. Such implementation has other problems before we even consider a variant. And, of course, this has nothing to do with visitation, specifically. The > exception safety guarantee is a global thing. Once you lose basic, you lose > it everywhere, not just for visit. > Why are you mentioning "basic" (guarantee) here? In the vision that I propose variant offers basic guarantee. It is just that the invariant is weaker. This is analogous to a (potentially smart) pointer: normally you can call `*p`, but sometimes (on nullptr) it is UB, so you may need to check what state it is in. Regards, &rzej;

2 2

Boost commercial support policy
by SOCIPROJECT 04 Apr '19

04 Apr '19

Hi,Good day.  This is Shuvransu Banerjee, development manager at Ushamartin Technologies. We build software products on Telecom Billing.We are at the planning level and thinking about using Boost in our legacy code. We have the following queries: Can we use Boost commercially? Is there any support available? If yes, then please let us know the various options for support.Thanks & Regards,Shuvransu Banerjee

2 1

B2, transition to C++
by Rene Rivera 04 Apr '19

04 Apr '19

After six months of, slowly, working towards this I can now say that the C++ compiled version of the B2 engine is ready for use. As such I plan, if there are no objections from Steven Watanabe and Vladimir Prus, to merge the result into the develop branch shortly after the 1.70 release. The history note accompanying this "new" engine version goes like this: === Version 4.0.0 After even more years of development the landscape of build systems has changed considerably, and so has the landscape of compilers. This version marks the start of B2 transitioning to a C++ implementation. Initially this means that the engine will be compiled as C++ source but that source is still the base C implementation. Over time it will transform to a C++ code base in both the engine and build system. Some changes in this start: * Requires C++ 11 to build engine. * Simplified build scripts to make it easier to maintain. * Building with C++ optimizations gives an immediate performance improvement. === There will obviously be bumps on the road when that merge goes in. As the C++ 11 requirement might require some changes for testers and users. But hopefully they will be minor. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net

2 1

Re: [boost] [variant2] Review of Variant2 started today : April 1 - April 10
by Peter Dimov 03 Apr '19

03 Apr '19

> Andrey Semashev wrote: > > Also, IMHO, it's better to have libraries more focused and fine grained. > > Why not have `expected` as a separate library? > > expected<T, E...> is basically a variant, with a slightly different > interface. To expand on that a bit... to implement expected<T, E...> you need an underlying variant. You can either implement your own ad-hoc one, which is a duplication of work; or you could use an existing variant, but then you inherit its properties and have to reflect those in the specification of `expected`. For instance, if the variant can be valueless, you need to figure out what to do in `expected` when it gets into that state. For those reasons, it makes most sense to develop `variant` and `expected` in parallel, as parts of the same library.

4 4

Master branch for 1.70.0 closes today!
by Marshall Clow 03 Apr '19

03 Apr '19

We're still in the post-beta phase, so please refer to < https://github.com/boostorg/boost/wiki/Releases%3A-Beta-Merge-Policy> -- Marshall

2 2

[gsoc19] Interested in Boost.Geometry PROJECT 2 (Support for non-cartesian)
by rika 03 Apr '19

03 Apr '19

Hi! I'm Rika from Japan, currently in 4th grade in the University of Tokyo. I'm going to take part in GSoC 2019, and interested in Boost.Geometry PROJECT2 - "Implement support for non-cartesin geometries in convex_hull()" I've already done a competency test, and writing a project proposal. [Competency test] https://github.com/rika77/boost I'm seeking for a mentor for this project. I also have 1 technical question & 1 general: 1. I'm afraid to ask, but what algorithm is currently used in convex_hull()? I read algorithms/convex_hull.hpp carefully, but I couldn't find out. 2. On GSoC GitHub page, there are 4 projects on Boost.Geometry, but are only 2 potential mentors. I guess that only 2 students are chosen, right? I just want to make sure. Thanks, Rika -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

4 3

Master branch open for merging
by Marshall Clow 03 Apr '19

03 Apr '19

The master branch is is now open for post-beta merges, but only as described in the Post-Beta Merge Policy. See < https://github.com/boostorg/boost/wiki/Releases%3A-Beta-Merge-Policy> -- The Boost Release Team

11 48

[gsoc19] late application for Boost.SafeFloat
by Thomas Ferrand 03 Apr '19

03 Apr '19

Hello, I am a student and I am interested in taking part of GSoC this summer. But I am a little late as the application are due to next week so I was wondering if I could still take part. The project I am interested in is Boost.SafeFloat, mentored by Damian Vicino. As for the competency test, it has already been taken care of as I believe it is the same that last year and I completed it then https://github.com/aTom3333/boost_competency_test/ Thomas Ferrand

4 4

Boost.Python
by Siddhartha Sen 02 Apr '19

02 Apr '19

Boost.Python does not have any added projects as of yet. I have completed my competency test and have a couple of ideas of my own.Need a potential mentor to discuss them with and review my proposal. Thanks.

2 1

[gsoc19] looking for mentor
by Aziz Mousa 02 Apr '19

02 Apr '19

hi, I have my idea to contribute in boost project, I read the boost libraries list and see that the author of Algorithm is "Marshall Clow" I want to know how to contact with him to tell him about my idea. thanks.

1 0

[gsoc][gsoc19] Communication between students and mentors
by Mateusz Loskot 02 Apr '19

02 Apr '19

Hi, Are there any guidelines related to communication between students and mentors during GSoC? Many participating organisations and projects do explicitly recommend that student/mentor communication is conducted via public channels. e.g. https://docs.moodle.org/dev/GSOC """ Note: With regards to the communication culture in the Moodle project: We always prefer transparent communication in public forums and tracker comments over private messages and emails. Please respect this and avoid contacting GSOC admins and mentors directly unless you really need to talk about something sensitive or personal. """ or at least regular/weekly reports to dedicated and project-specific list https://wiki.osgeo.org/wiki/Google_Summer_of_Code_Recommendations_for_Stude… Would it be possible to ask for similar transparent mode during Boost GSoC? I do realise one challenge is that Boost mailing list traffic could increase a lot, too much for some subscribers. Perhaps a solution to that could be setting up dedicated lists: gsoc(a)lists.boost.org or even <library>@lists.boost.org Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

2 2

(no subject)
by Aziz Mousa 02 Apr '19

02 Apr '19

hi, I submit my proposal draft on GSoC and I want to know how to meet a mentor to see my proposal.

3 2

[gsoc19] Seeking a mentor for Boost.GIL project
by Igor Antropov 02 Apr '19

02 Apr '19

DearSir/Madam, My name isIgor Antropov and I would like to participate in GSoC 2019.I amfirst-year undergraduate master majoring in Software Engineering at ITMOUniversity (Saint Petersburg National Research University of Information Technologies,Mechanics and Optics).I aminterested in computer vision and C++. I have made AR-application using Unityand OpenCVForUnity at my third-year of bachelor degree. Unfortunately, thatOpenCVForUnity was based on OpenCV version 2.1 or smaller and was the only onefree to use. There was no algorithm for markers detection, so I had to codeit. At the fourth-year, I have implementobject tracking algorithm with C++ and OpenCV using HOG features and colornames features. Additionally, I havebeen working as programmer with Qt for 1 year. I aminterested in implementation of different algorithms using GIL, so I propose toimplement some image feature detection and matching algorithms. For example,ORB keypoints detector(http://www.willowgarage.com/sites/default/files/orb_final.pdf) and brute-forcematching. Besides, I think Boost.GIL numeric algorithms can have some improvements (add 2D convolution, add convolve_option_extend_reflect as convolve_boundary_options). If Boost.GIL users need some other algorithms to be implemented,please contact me. As my competencytest, I have implement a simple Canny edge detection algorithm using GIL. https://github.com/boostorg/gil/pull/258 Sincerely, IgorAntropov

2 1

[GSOD] Looking for mentors and projects
by Damian Vicino 02 Apr '19

02 Apr '19

Hi, I'm starting preparing the application for Google Season of Docs 2019. I created a wiki page to start collecting project ideas here: https://github.com/boostorg/boost/wiki/Google-Season-of-Docs-2019 Instruction of how to write a project idea are here: https://developers.google.com/season-of-docs/docs/project-ideas Please add any idea you have, even if you are not able to mentor it, someone else may volunteer for it. Best regards, Damian Vicino

4 4

[gsoc19] Seeking a mentor for Boost.Geometry project related to triangulation and random sampling
by Tinko Bartels 01 Apr '19

01 Apr '19

Hi, I am interested in participating in this year's Google Summer of Code with a contribution to Boost.Geometry. I am looking for mentors and I understand that potential mentors for Boost.Geometry-related projects are Vissarion Fysikopoulos and Adam Wulkiewicz. My proposal is a project that is based on project 3 and 4 for Boost.Geometry in the Wiki. I propose to add concepts for triangles, triangulation, and point-generators for random sampling, as well as corresponding models and an algorithm for Delaunay-triangulation with parametrizable geometric predicates. The first draft of my proposal can be found here: https://docs.google.com/document/d/17M44Hpn0KMuECztCbkvTYIeN2EiXbMAUsVni22K… My implementation of the tasks in the competency tests can be found here: https://tinko92.github.io/boost_geometry_GSoC_2019_project_3_4_test/ I'd be thankful for any feedback. Kind regards, Tinko Bartels -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

3 10

[gsoc 2019]proposal to Boost.GIL project 1
by raghuchandra kanakamedala 01 Apr '19

01 Apr '19

Hi Please give me your feedback on my proposal to increase my chases of participation in the project. link: https://docs.google.com/document/d/1-BZO0VuIcebe1ZcdyxHGjOEkQL3eeaXwGtKCWyQ… Thank you K RaghuChandra

1 0

[GSOC 19]Boost.GIL
by raghuchandra kanakamedala 01 Apr '19

01 Apr '19

Hi Is there a mentor for Boost.GIL.If so please send me his/her email id. Thanking you K RaghuChandra

1 0

[format] Allow the format library to use std::optional
by Sean Farrow 30 Mar '19

30 Mar '19

Hi, Would be possible/desired to allow boost.format to use std::optional instead of boost.optional when compiling a C++17 project. I've raised a GitHub issue to resolve this: https://github.com/boostorg/format/issues/63 I would be happy to do this if it were warranted. Kind regards Sean.

1 0

Re: [boost] [Boost-build] Building Boost 1.69 with Visual Studio 1.69
by Steven Watanabe 29 Mar '19

29 Mar '19

AMDG On 3/27/19 12:02 PM, Paul Bristow wrote: >> <snip> > I was fully up-to-date on develop yesterday, and installed git a week ago (new machine ;-) ). > The current revision of Boost.Build in develop should be e22a75c8 (March 18) > I am also slightly concerned that specifying the cl.exe fully may not be updated when Visual studio is updated, as happens today? > But it does seem to using the new compiler version, even though the full cl.exe file specification is no longer correct. > Similarly vsvarsall.bat location in the set command will change. > > But I am getting Boost library files built OK for several compilers and versions, so that's progress. > Hmm. It looks like VS2019 isn't being autodetected. It seems to be working for Tom's test runners. Maybe see what you get from: vswhere -latest -products * -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property installationPath -version "[16.0,17.0)" (This is how Boost.Build tries to detect VS2019.) In Christ, Steven Watanabe

6 12

Regarding BOOST.Astronomy
by Sarthak Singhal 29 Mar '19

29 Mar '19

Hello everyone, I am not able to understand what exactly is to be done to complete the parser for FITS and I have also tried understanding the codebase but I am not getting what is the work done till now. Can you also provide some resources? Thanking you Sarthak Singhal

4 3

[visibility][test][osx] visibility warnings with 1.70beta
by Raffi Enficiaud 28 Mar '19

28 Mar '19

Hi, I have a side project that requires boost.test and I thought it is the right time to use the beta build of 1.70. At link time for my project (in this case a simple boost.test module), I have tons of warnings like the following: ld: warning: direct access in function 'boost::unit_test::decorator::depends_on::apply(boost::unit_test::test_unit&)' from file '/Users/raffi/from-big-laptop/code/software_workshop/sw_thirdparties/osx/boost_1_70_0_b1/lib/libboost_unit_test_framework-xgcc42-mt-x64-1_70.a(decorator.o)' to global weak symbol 'boost::unit_test::basic_cstring<char const>::null_str()::null' from file '/Users/raffi/code/mpi/mpi_kmeans/build/MPI-Kmeans.build/Debug/test_mpi_kmeans.build/Objects-normal/x86_64/test_cls_and_func_impl.o' means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings. running Xcode 10.1 on 10.14/mojave. I am building boost like this: ./b2 \ cflags="-mmacosx-version-min=10.10" \ cxxflags="-std=c++11 -stdlib=libc++ -mmacosx-version-min=10.10" \ mflags="-mmacosx-version-min=10.10" \ mmflags="-mmacosx-version-min=10.10" \ linkflags="-stdlib=libc++ -mmacosx-version-min=10.10" \ --prefix=`pwd`/../${build_folder} \ --without-log \ --layout=versioned \ install Each of the files that are being built in my project and that are raising the warning have a compilation command like this: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -DBOOST_ALL_NO_LIB -DKMEANS_VERBOSE=0 -I/Users/raffi/code/mpi/mpi_kmeans/include -I/Users/raffi/code/mpi/mpi_kmeans/applications/include -isystem /Users/raffi/from-big-laptop/code/software_workshop/sw_thirdparties/osx/boost_1_70_0_b1/include/boost-1_70 -O3 -DNDEBUG -std=gnu++11 -o CMakeFiles/test_mpi_kmeans.dir/test/test_kmeans.cpp.o -c /Users/raffi/code/mpi/mpi_kmeans/test/test_kmeans.cpp which is pretty much what I had so far and before 1.70. Boost.test is using BOOST_SYMBOL_VISIBLE to make a symbol public, including the static build variant. Why does the linker say """ This was likely caused by different translation units being compiled with different visibility settings. """ is completely unclear to me. How can I inspect what b2 emits as compilation command line for further debugging? All those visibility issues are causing me a lot of headache :) Thanks! Raffi

3 5

Gsod19 interest
by Damian Vicino 27 Mar '19

27 Mar '19

I'm wondering if there is interest to make boost participate in the Google season of docs. The program is similar to Google summer of code in many ways, but the outcome is production of documentation. It Details: g.co/seasonofdocs <https://developers.google.com/season-of-docs/>

5 15

[GSOC 2019]
by shehab alaa 27 Mar '19

27 Mar '19

Hi, I’m student willing to participate in GSOC 2019. I have finished my competency test for Boost.uBLAS and I have interest in projects 2 (Adding new numerical linear and multilinear algebra algorithms).So I’m writing looking for mentor who have interest to guide me. And here is my GitHub link for competency test https://github.com/Shehabalaa/CompetencyTest Best regards, Shehab Alaa

2 1

Re: [boost] [review][variant2] Variant2 Review Starts April 1
by dariomt＠gmail.com 26 Mar '19

26 Mar '19

> > The class boost::variant2::variant<T...> is an almost conforming > implementation of std::variant with the following differences: > I see the useful comparison to std::variant in the doc, however I'm using boost::variant extensively in my code. It would be very useful to have also a short comparison to boost::variant in the doc, as I would expect many more current users of the venerable boost::variant than of its much younger cousin std::variant. Thanks!

6 8

Building Boost 1.69 with Visual Studio 1.69
by Trueman, Chris 26 Mar '19

26 Mar '19

Maybe I'm getting ahead of myself given the recent topic about picking a version number for the latest MSVC toolset but I'm having trouble building boost 1.69 with Visual Studio 2019 preview. I blindly assumed the toolset was 14.20 (given the directory where cl.exe is found). Letting b2 determine the version yields vc141 in the lib names. Trying to force 142 with: using msvc : 14.2 : <path to cl.exe> ; in project-config.jam yields errors about unescaped characters. Suggestions welcomed. Chris. INTELLICORP LEGAL NOTICE: This E-Mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying or other use of this message or its attachments is strictly prohibited. If you received this message in error, please notify the sender immediately by replying to this message, and then delete it.

6 11

[fibers] Great amount of errors and warnings raising out of valgrind
by Stephan Menzel 26 Mar '19

26 Mar '19

Hello all, I was just in the process of doing vagrind runs on a server process that recently switched to an architecture using boost fibers. Specifically buffered_channel as a number of worker fibers run in a thread. The process was regularily checked with valgrind before but now I'm getting overwhelmed by the amount of messages. Uninitialized values, invalid writes and reads all across the board and all seem to come out of fibers. I see no direct mention of my code. A few samples: ==8024== Thread 1: ==8024== Conditional jump or move depends on uninitialised value(s) ==8024== at 0x454F98: unique (circular_list_algorithms.hpp:112) ==8024== by 0x454F98: empty (list.hpp:540) ==8024== by 0x454F98: boost::fibers::buffered_channel<std::function<void ()> >::close() (buffered_channel.hp ==8024== by 0x454FDB: boost::fibers::buffered_channel<std::function<void ()> >::~buffered_channel() (buffere ==8024== by 0x4376BF: operator() (unique_ptr.h:78) ==8024== Invalid read of size 8 ==8024== at 0x9C1756: boost::fibers::context::~context() (in /my_server) ==8024== by 0x9C31CF: boost::fibers::main_context::~main_context() (in /my_server) ==8024== by 0x6B0B85E: __call_tls_dtors (in /usr/lib64/libc-2.26.so) ==8024== by 0x5D49558: start_thread (in /usr/lib64/libpthread-2.26.so) ==8024== by 0x6BC92FE: clone (in /usr/lib64/libc-2.26.so) ==8024== Address 0xa6f0010 is 32 bytes inside a block of size 232 alloc'd ==8024== at 0x4C2D1DA: operator new(unsigned long) (vg_replace_malloc.c:334) and thousands more similar to this. Now, is there something about fibers that causes this as false positives (such as valgrind not knowing about fibers or coroutines) or is there an underlying problem here? This is running on AWS Linux 2, built with gcc 7.3, boost 1.69. Multithreaded release build with debug info. Nothing out of the ordinary. I am a bit concerned about this and wanted to let the list know. Can provide more output on demand. Cheers, Stephan

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Re: [boost] [review][variant2] Variant2 Review Starts April 1
by dariomt＠gmail.com 26 Mar '19

26 Mar '19

> > On Mon, 25 Mar 2019 at 17:18, dariomt--- via Boost <boost(a)lists.boost.org> > wrote: > > > ... as I would expect many more current users of the venerable > > boost::variant than of its much younger cousin std::variant. > > > > Why do you expect that and do you think that will stay that way? Well, Boost.Variant has been around so much more time than std::variant, so this seems obvious to me. For new code, maybe people will just use std::variant, but there's more old code than new code. Also, I'd say the cost of migrating from Boost.Variant to std::variant is non-zero, and the benefits are not clear (to me), so I'd expect not many people to undergo this migration. My feeling is that the library is aimed at current users of std::variant, offering a "better" pin-compatible alternative, but if I'm using Boost.Variant I believe I also should be considered a potential user. That's why I'm curious about the Boost.Variant2 review, we might get more clarity by comparing the three versions, and we may even get guidance for a migration path from Boost.Variant to Boost.Variant2. > My > personal feeling is that C++17-use is picking up at break-neck speed. For > good or for worse, although there appears to be a lot of controversy over a > (any) variant [and there are quite some quite different implementations > around], the std::variant is the one in the std, which seems to give it a > head start. Well, in my (limited) experience Boost is ubiquitous, so being in std is not that much of a head start. > In my view there can only be one objective with boost varant2, > and that is if it is decided [here] that it is (much) better than the > current std::variant, the C++20 std::variant should be/become the proposed > boost::variant2. > > degski > I wonder if code dealing explicitly with valueless_by_exception() will break if you make this change.

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Re: [boost] [review][variant2] Variant2 Review Starts April 1
by dariomt＠gmail.com 26 Mar '19

26 Mar '19

> > dariomt--- wrote: > > > The class boost::variant2::variant<T...> is an almost conforming > > > implementation of std::variant with the following differences: > > > > > > I see the useful comparison to std::variant in the doc, however I'm > using > > boost::variant extensively in my code. > > > > It would be very useful to have also a short comparison to > boost::variant > > in the doc, as I would expect many more current users of the venerable > > boost::variant than of its much younger cousin std::variant. > > The main difference is that Variant2 is a pin-compatible replacement for > std::variant, whereas Boost.Variant isn't (at least for now). So it's > easier > to switch from std::variant to Variant2 and back (depending f.ex. on > whether > std::variant is available.) > > The second most important difference would probably be the fact that > Boost.Variant may do heap allocations. > This is useful info, thanks! I understand that the main objective is to offer a "better" std::variant, but as a user of Boost.Variant wondering "Should I consider migrating to Boost.Variant2?", I would expect a section in the doc addressing this question.

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Which forum to handle issues/questions regarding libraries
by Robert Ramey 25 Mar '19

25 Mar '19

I've been studying the boost multiprecision library and I have a few questions relating to various aspects of said library. These questions are quite specific to that library and I'm not sure that they are of wider interest other than to a couple people. So I'm wondering if it would be better to post these as library issues on github or on this list or both. It used to be simple but now we have at least three places to discuss these things: slack, here and github issues for the library in question. Also sometimes some PRs can highlight differences which can get ironed out in the PR comments. Do we have a consensus as to the preferred way to select the correct forum? Robert Ramey

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Looking for a Mentor: GSoC 19: Boost.uBLAS: Linear and Multilinear...: Project 1 and 2
by forcha glen 24 Mar '19

24 Mar '19

Hello, I am interested in any of these two projects. I do not yet have a mentor. I need mentor. Regards, Glen

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Re: [boost] Master branch open for merging
by Nikita Kniazev 22 Mar '19

22 Mar '19

I would like to merge Spirit to master. The develop contains bunch of minor changes, but I important ones are: Endian namespace pollution and macros conflict fixes: https://github.com/boostorg/spirit/commit/6c258d506c2bbadccdb9f25e481984aca… https://github.com/boostorg/spirit/commit/74c0ec310a2345cb95ffb947327f69007… https://github.com/boostorg/spirit/commit/9d48b5a23197bbbcc4a3a8990c164b1cf… GCC 6/7 regression avoidance: https://github.com/boostorg/spirit/commit/8bd9b6ece40f9324a902bb0f726e785ff… The regression matrix is green for two weeks.

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[release] Boost 1.70.0 Beta 1 is now available
by Marshall Clow 22 Mar '19

22 Mar '19

[ resending with a non-empty subject line ] Boost release 1.70.0 beta 1 is now available at: <https://dl.bintray.com/boostorg/beta/1.70.0.beta1/source/> The SHA256 checksums are as follows: dbf89645e509acb2e53eac3c633834f1dec80bd8622e6e652a9741dcf0807f17 ./boost_1_70_0_b1.7z 957b984b58656a3ec00661ecad7ef82e3a094bad36e37b9e6624843237854679 ./boost_1_70_0_b1.tar.bz2 76d149c1fb9e8a5ceb3bc1e5587edc40fa79a43e8b990d877c2210f0382b9421 ./boost_1_70_0_b1.tar.gz 71e990b2c26880521fd98459b184ee172ce1c46dcf554b6eaab7776b8b6369a6 ./boost_1_70_0_b1.zip For details of what's in the release, see < https://www.boost.org/users/history/version_1_70_0.html>. Please download the beta, give it a try, and report any problems you encounter. Thanks, -- The Boost Release Team

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[Process] Proposed solution for posix pipes staying open
by Bills, Jason M 22 Mar '19

22 Mar '19

Hello, I'm new to Boost and looking for some help on the right process to propose patches. I'm running in an embedded Linux environment (OpenBMC) using Boost 1.69.0 and just switched a couple of std::system() calls to boost::process::system() calls. After making this change, I noticed that each time my process executed the bp::system() call, I would get an extra pipe fd in my /proc/<pid>/fd list. I did some debugging and have found a possible solution for this issue in the Boost.Process posix headers that I would like to propose. What is the right forum or process to post my patch (post it here, github pull request, etc.)? Thanks! -Jason

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questions about boost multiprecision
by Robert Ramey 22 Mar '19

22 Mar '19

I'm looking more carefully at Boost Multiprecision than I have in the past and have a couple of questions: It's not clear to me how errors are handled. For example, what happens in a divide by zero? Or what happens when a result overflows. I'm aware that this will likely vary depending on whether the arguments are arbitrary precision made a runtime or a precision fixed at compile time. In any case, looking through the manual I can't find this information. Of course this package is so ambitious, that it's possible that I've missed it but in that case a pointer would be appreciated. Spending some time on this makes me appreciate what an incredibly ambitious accomplishment this is. It's really unbelievable. I would be curious how frequently various parts of the package are used. Robert Ramey

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usage of auto in tutorials
by Stephan Menzel 22 Mar '19

22 Mar '19

Hello all, I was eagerly awaiting the release of the 1.70 beta, especially for outcome, which I have much use for, having lots of async functionality. While looking at the tutorial here that https://www.boost.org/doc/libs/1_70_0_beta1/libs/outcome/doc/html/index.html I notice that auto is used instead of the types. Is there a background to this? I question if this is such a good thing in tutorials. The first thing I like to know about a new lib is the types and classes it offers and auto obfuscates this. Is there any consensus in the boost community as to how and if tutorials and docs should use auto? I have concerns about this and feel it doesn't increase the otherwise great quality of documentation and tutorials for new libs. Cheers, Stephan

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[test] unit test command-line handling
by Stefan Seefeld 22 Mar '19

22 Mar '19

Hello, this is a question concerning the Boost.Test framework. I'd like to pass command-line arguments to my tests, and I'm unsure of how to proceed. I have found https://www.boost.org/doc/libs/1_68_0/libs/test/doc/html/boost_test/adv_sce…, which shows how to access the command-line programmatically, but that's declared obsolete, and it's also lacking some important info, such as how I should handle the argv vector. Are there any examples that demonstrate this use case ? Specifically: * What (non-deprecated) API can I use to access command-line arguments during test initialization ? * How does my own handling of command-line arguments interact with Boost.Test's own command-line argument handling ? Thanks, Stefan -- ...ich hab' noch einen Koffer in Berlin...

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[move] Bug causing issue #81 in Interprocess
by Ion Gaztañaga 21 Mar '19

21 Mar '19

Hi, Looks like a Boost.Move bug that is causing problems in Interprocess and potentially in other libraries like Container. The bug is present in the soon to be released Boost 1.70. The bug was reported by Nikita Kniazev for Interprocess: https://github.com/boostorg/interprocess/issues/81 I've committed a simple fix in the develop branch: https://github.com/boostorg/move/commit/756c964798ff1110406fab541b85267aefb… I hope the regression can cycle soon and release managers can approve the patch for Boost 1.70. Best, Ion

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[GSoC 2019] Seeking guidance for Boost.uBlas (Project 4)
by livingstonegcs 21 Mar '19

21 Mar '19

Hello Boost community, I am GCS Living Stone, a Computer Science and Engineering undergraduate at National Institute of Science and Technology. I have fair amount of knowledge in Linear Algebra and skills in C++, Python programming. I have gone through Boost GSoC2019 proposal list. I found interest in Boost.uBlas Project 4: Non-negative matrix factorization implementation. I am seeking information regarding where to submit the competency test and how to begin with the project proposal as the project description has not mentioned any specific techniques. [Also I would like to bring to your notice that the Boost.Python project just mentions the project number but does not describe the projects.] Looking forward for the advice and guidance in the mentioned issue. Thanking you, GCS Living Stone -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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GSoC : Boost.Geometry: Generic Geometry Library
by Sarah Arrey 20 Mar '19

20 Mar '19

Dear Sir/Madame, My name is Sarah Arrey. I am a student in the University of Buea, Cameroon. I have written professional programs in C++. As a result of my Anglo-Saxon culture, and currently in the faculty of science, I have good knowledge in mathematics beyond that of the high school; my country is Bilingual (English and French). I am interested in applying for the following two projects: PROJECT 3: Implementation of Algorithms for Computing the Delaunay Triangulation PROJECT 4: Implementation of Algorithms for Random Point Generation I am willing to forward code for the Programming Competency Test, when applying. How do I get started? Regards, Sarah

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GSoC 2019 - Boost.Geometry: Generic Geometry Library
by Indira Ngandi 20 Mar '19

20 Mar '19

Hello, I am Indira Ngandi, a Cameroonian (not an Indian). I am a student in the University of Buea, Cameroon. I have good knowledge in C/C++. I also have good knowledge in British Further Mathematics. I am interested in applying for the following two projects. I know that only one can be accorded to me. I would like to apply for two to improve my chances of having one. The projects are: PROJECT 1: Implementing Algorithms for the Concave Hull problem PROJECT 2: Implementing Support for Non-Cartesian Geometries in Convex_Hull How do I start? Regards, Indira

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Regarding BOOST.Astronomy GSOC'19
by Sarthak Singhal 20 Mar '19

20 Mar '19

Hello everyone, I am Sarthak Singhal currently in my second year pursuing Computer Science and Engineering from IIT Kanpur. I have checked out the astronomy library of boost and the work done on it in previous year's GSOC. I am interested in making contributions to this library. I am proficient in C++ and have an experience of about one and a half years. But before that I want to complete the programming competency test and wanted to know that whether I have to implement the vector class from scratch or I have use the part of boost/astronomy/coordinate/cartesian_representation.hpp and some other header files.

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GSoC Linear and Multilinear Algebra with Matrix and Tensor Computations
by forcha glen 19 Mar '19

19 Mar '19

Hello, I am Glen Beloa. I am a student in the University of Buea, Cameroon. I am studying for a Master's degree in Telecommunications and Networking. I understand that I can apply for two projects. I would like to apply for the projects: Project 1 : Extending and modifying boost::numeric::ublas::tensor Project 2 : Adding new numerical linear and multilinear algebra algorithms How do I get started? Regards, Glen

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GSoC Linear and Multilinear Algebra with Matrix and Tensor Computations
by forcha pearl02 19 Mar '19

19 Mar '19

Hello, I am Pearl Fri. I am a student in the University of Buea, Cameroon. I am studying for a BEng degree in Computer Engineering. I would like to apply for the following two projects: Project 3 : Modifying (smart) expression templates Project 4: Implementing non-negative matrix factorization in uBlas How do I get started? Regards, Pearl

1 0

MSVC 2019 and 1.70 beta
by Olaf van der Spek 19 Mar '19

19 Mar '19

Hi, Is 2019 not properly supported yet? > Building Boost.Build engine > 'cl' is not recognized as an internal or external command, > operable program or batch file. > Failed to build Boost.Build engine. > Please consult bootstrap.log for further diagnostics. >From a dev prompt it doesn't appear to work either: ********************************************************************** ** Visual Studio 2019 Developer Command Prompt v16.0.0-pre.4.2 ** Copyright (c) 2019 Microsoft Corporation ********************************************************************** C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview>cd /vc C:\vc>cd boost_1_70_0 C:\vc\boost_1_70_0>bootstrap.bat Building Boost.Build engine Generating Boost.Build configuration in project-config.jam for msvc... Bootstrapping is done. To build, run: .\b2 To generate header files, run: .\b2 headers To adjust configuration, edit 'project-config.jam'. Further information: - Command line help: .\b2 --help - Getting started guide: http://boost.org/more/getting_started/windows.html - Boost.Build documentation: http://www.boost.org/build/ C:\vc\boost_1_70_0>b2 warning: Did not find command for MSVC toolset. If you have Visual Studio 2017 installed you will need to specify the full path to the command, set VS150COMNTOOLS for your installation, or build from the 'Visual Studio Command Prompt for VS 2017'. Performing configuration checks - default address-model : none - default architecture : none Building the Boost C++ Libraries. error: No best alternative for libs/context/build/asm_sources next alternative: required properties: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>clang not matched next alternative: required properties: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>gcc not matched -- Olaf

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I am interested to participate in BOOST GSOC2019 project
by raghuchandra kanakamedala 19 Mar '19

19 Mar '19

Hi I am Raghuchandra studying 3rd year B.Tech at IIIT Hyderabad. It would be great to contribute to Boost.GIL: generic image library.I have ideas for both the projects.I had this course Digital Image Processing also done a project "Road detection from satellite images" based on the paper attached.my implementation link to git https://github.com/savera2020/dip_project/ .I have good skills in C++ programming. so can you provide the mail id of mentor so that we can go more deeper about the project.please consider my request to contribute to project.without a doubt i will give my best. best regards Raghuchandra

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GSoC 2019 preparation , BOOST.uBLAS project
by mo'men 18 Mar '19

18 Mar '19

Hi, I’m Moamen Ahmed , 4th year student at computer engineering department at Ain Shams university ,Cairo, Egypt. I have read the interesting project ideas , and I have found myself interested in BOOST.uBLAS project. Also, I have good experience in Linear Algebra , and C++ programming. I have developed c++ projects on my own and still do . I ‘m trying now to make the competency test. I 'd like to join BOOST.uBLAS project ,so kindly , help me through the process on how to enhance my opportunity to join this project . Best regards, Moamen Ahmed

2 1