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Re: [boost] [Describe] Boost.Describe vs Boost.Fusion
by Nikita Kniazev 02 Mar '21

02 Mar '21

> Or have Spirit perform a check: if `describe::members` is found use it, otherwise fall back to Boost.Fusion. Spirit uses Fusion iterator_range internally, it will require to find/write a replacement that will work with both libraries.

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AVL Databases and Boost Serialization in C++
by Benedict NNcNannara 02 Mar '21

02 Mar '21

AVL Databases were invented in C# and Java in 2016. More recently (2022) AVL Databases were invented in C++. They were a port of the C# code back to C++. In fact, the port was of a larger system - The Generic Language. Boost Serialization Library was used to serialize a general datatype t in set<t>. This applies to the C++ Variant of AVL Databases, The Generic Language Compiler uses AVL Databases to store its code. Execution occurs directly out of the code database, thus no loader is required. In fact the multithreaded, monolithic runtime is very fast compared to the C# version which is now obsolete. uuindouus.zip <https://drive.google.com/file/d/1NhEEmfZMf5yGbnsTAHH1N-XAjPCbczAy/view?usp=…>

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1.76 schedule?
by John Maddock 01 Mar '21

01 Mar '21

Just noticed that the calendar has master closed for breaking changes from yesterday... I was hoping to do a Math & Multiprecision release, but they drop C++03 and have some massive restructuring/changes as a result. On the plus side they're better tested than they probably ever have been. So... too late for 1.76 or not? Thanks, John. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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feature for C++ standards compliance
by Robert Ramey 28 Feb '21

28 Feb '21

The serialization library is compatible with C++03 (and likely 98). And is tested regularly with C++ compilers with the -std switch set to this mode. The recent changes to the math library have broken about 5 tests in the serialization library. Since this breakage is in a few tests only and not in the library itself, I'd like to suppress these tests when the being tested with a C++03 compiler. I've suppressed tests which are conditional on C++ features which are not supported and this has worked well for my purposes. I'd like to do the same for a couple of tests which are conditional on usage of the math library and standards versions < C++11. Any B2/CMake experts want to help an old guy out?

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New PropertyTree maintainer
by Glen Fernandes 27 Feb '21

27 Feb '21

Richard Hodges has kindly agreed to become the new maintainer of Boost.PropertyTree. Many thanks, Richard. Please update meta/libraries.json accordingly. Glen

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Google Summer of Code follow-up
by Radu Cosma 26 Feb '21

26 Feb '21

Dear all, A couple of weeks ago I wrote an email inquiring about how to approach applying to contribute to your project through the GSoC opportunity. I did not seem to get any responses, is this the right place to ask? If not, could you please point me to a contact person that I can talk to? I am very interesting in contributing to this project and would really like to know how I can help. I am extremely familiar with the entirety of the C++20 standard, besides some final template (and concepts) features that I am still learning about, and would love the challenge of using those skills in the context of contributing to the Boost libraries. Thank you in advance and have a nice day! Kind regards, Radu Cosma

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Introduction
by Samrat Patel 25 Feb '21

25 Feb '21

Hello Boost C++ Community, I am Samrat from Delhi Technology University and currently, I am pursuing my bachelor's in Computer Engineering(CoE). I have 3 years of experience in C++. I am extremely eager and excited about contributing to various projects of Boost C++. I am willing to participate in GSOC'21 with Boost C++. I would feel indebted if you could guide me in this regard. Regards Samrat Patel

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property_tree in need of a maintainer
by Richard Hodges 25 Feb '21

25 Feb '21

Dear all, I am offering to become the/a maintainer of property_tree as part of my work for the C++ Alliance. Sincerely, -- Richard Hodges hodges.r(a)gmail.com office: +442032898513 home: +376841522 mobile: +376380212

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Reminder: Describe needs a review manager
by Peter Dimov 25 Feb '21

25 Feb '21

This is a reminder that my library Describe https://github.com/pdimov/describe https://pdimov.github.io/describe/doc/html/describe.html needs a review manager. Describe is a library that allows programmers to annotate their classes (and enumerations) in order to enable simple reflection. It provides a very important fundament on which other libraries can build upon to provide automatic support for user-defined types. For example, given an annotated type, Boost.JSON can automatically provide conversions from/to json::value. Boost.ContainerHash can automatically provide a hash function hash_value for the type. Boost.Serialization can automatically provide serialization support. See the examples: https://pdimov.github.io/describe/doc/html/describe.html#example_to_json https://pdimov.github.io/describe/doc/html/describe.html#example_from_json https://pdimov.github.io/describe/doc/html/describe.html#example_serializat… Other JSON (and serialization) libraries already offer a similar mechanism, e.g. https://github.com/nlohmann/json#arbitrary-types-conversions. But since each library has its own private way to annotate types, a programmer needs to repeat the type annotations for every library he wants his type to be known to. This is unnecessary and undesirable, and a standard mechanism to describe types avoids it. Describe is intended to be this standard mechanism, and I believe that we need it in Boost sooner rather than later. Thanks in advance to whoever volunteers.

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Re: [boost] Reminder: Describe needs a review manager
by Bjorn Reese 25 Feb '21

25 Feb '21

On 2021-02-23 19:56, Peter Dimov via Boost wrote: > Describe is a library that allows programmers to annotate their classes > (and enumerations) in order to enable simple reflection. It provides a > very important fundament on which other libraries can build upon to > provide automatic support for user-defined types. How does it differ from Boost.Fusion?

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[boost-ext] Looking for Review Manager/s
by Krzysztof Jusiak 24 Feb '21

24 Feb '21

Hi, I just wanted to share, potentially useful for the Boost and C++ community, libraries and ask if anyone would be willing to become a Review Manager for any of them? [boost-ext] (https://github.com/boost-ext) is a collection of C++ libraries with aspirations to be included in Boost. Libraries can be characterized by: * Modern C++ (>= C++14) * Header/Single Module only * No dependencies ATM, [boost::ext] consists of four core libraries: * DI - Dependency Injection Library overview: standard: C++14 single header with no dependencies (neither STL nor Boost is required) release: 1.2.0 (first release - 2014) key features: - supports macro-free constructor injection - supports templates injection - quick compilation-times - highly optimized code generation try it online: https://godbolt.org/z/5qTKhf source code: https://github.com/boost-ext/di documentation: https://boost-ext.github.io/di/ * SML - State Machine Library overview: standard: C++14 single header with no dependencies (neither STL nor Boost is required) release: 1.1.4 (first release - 2016) key features: - much faster compilation-times than Boost.MSM (up to 60x faster) - highly optimized and customizable code generation - suitable for embedded systems try it online: https://godbolt.org/z/y99L50 source code: https://github.com/boost-ext/sml documentation: https://boost-ext.github.io/sml/ * UT - Unit Testing Framework overview: standard: C++20 single header with no dependencies (STL required) release: 1.1.8 (first release - 2019) key features: - macro-free - minimal boilerplate - fast compilation-times and execution try it online: https://godbolt.org/z/Jqb5Ye source code: https://github.com/boost-ext/ut documentation: https://boost-ext.github.io/ut * TE - Run-time polymorphism (type erasure) library overview: standard: C++17 single header with no dependencies (STL required) release: - key features: - simple interface - highly optimized code generation try it online: https://godbolt.org/z/xY9MEq source code: https://github.com/boost-ext/te documentation: https://github.com/boost-ext/te All libraries (except TE) were successfully deployed in the production systems. Some, such as DI and SML are used by well known/big IT companies as well. If anyone is interested in becoming a Review Manager for any of the libraries, I'd really appreciate it and I'll more than happy to address any issues/requests before the review as well as help with any process-related tasks. Thank you very much, -Kris

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Getting stated with boost and CMake
by pbristow＠hetp.u-net.com 24 Feb '21

24 Feb '21

Having spent a decade watching the Cmake versus bjam/b2 battle, I had thought it wise to wait until the dust has settled. It would appear that the enthusiasm for CMake and Boost is much greater among consumers than producers ☹ But recently I have been working on a project that is possible Boost library and thought that I would dip my toe in the water. After some research, I am still puzzled how I should replace a simple b2/bjam program (say a classic “hello World”) that is run like this \example > b2 -a toolset=msvc,gcc,clang cxxstd=14 release > my_log.log The jamfile contains run hello_world.cpp ; # Simplest hello_world, no other includes apart from iostream. And the b2 run .log contains some outputs of "Hello world" and 3 nice **passed** lines and ...updated 3(?) targets..., one for each compiler (and version too, perhaps with some potentially using build info too), and return exit_success value. (I also would expect to get a simple setup to run a test using the /included version of unit_test_framework. Trying to walk before I fall over running, I have avoided any pre-compiler libraries, at least at first.) After some research (getting as far as generating a Visual Studio project, where I can intervene manually to build and run my hello_world program), I am still unclear how to replicate this b2 test to end with a .exe run and some log file with pass/fail indications. I am of course building on Windows 10 with three recent versions of MSVC, GCC and Clang compilers working, and in my bjam/b2 user-config.jam. Advice from less-than-novice CMakers most welcome. Thank you. Paul

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GSoC 2021 new policies
by Pranam Lashkari 23 Feb '21

23 Feb '21

Hello, To all the potential mentors and students this year GSoC is different from all the previous seasons, so whenever you are planning/proposing/adding a project in GSoC this year, keep the following things in mind: *Smaller project size** - *all students participating in the 2021 program will be working on a 175 hour project (instead of a 350 hr project). *Shortened coding period* - the *coding period will be 10 weeks* with a lot more flexibility for the mentor and student to decide together how they want to spread the work out over the summer. *2 evaluations (instead of 3)* - There will be an evaluation after 5 weeks and the final evaluation will take place after the 10th week. -- Thank you, Pranam Lashkari, https://lpranam.github.io/

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Releasing property_tree updates
by Jared McIntyre 20 Feb '21

20 Feb '21

I noticed there are several updates that have merged into the develop branch for property_tree, but it seems none of them have made it into master for release. Is there any chance that a new version with the fixes may be pushed out in a future release? Thanks, Jared

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boost test: first test organization examples using deprecated init_unit_test_suite?
by Dennis Luehring 15 Feb '21

15 Feb '21

according to this example, i should use init_unit_test_suite https://www.boost.org/doc/libs/1_75_0/libs/test/doc/html/boost_test/tests_o… but it seems that init_unit_test_suite function is deprecated (starting with 1.59) https://www.boost.org/doc/libs/1_75_0/libs/test/doc/html/boost_test/adv_sce… so its unclear to me if i should (still) use this deprecated function or go witht BOOST_AUTO_TEST_SUITE/BOOST_AUTO_TEST_CASE

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[build] "Unknown target type EXE"
by John Maddock 09 Feb '21

09 Feb '21

I've managed to get various architectures tested in qemu-emulation in this PR: https://github.com/boostorg/config/pull/366, with help from https://github.com/uraimo/run-on-arch-action However, for armv7 alone I see: /home/runner/work/config/boost-root/tools/build/src/build/type.jam:158: in type.validate from module type error: Unknown target type EXE (builtin):-1: in sequence.transform from module sequence /home/runner/work/config/boost-root/tools/build/src/build/generators.jam:239: in generator.__init__ from module object(installed-exe-generator)@4 /home/runner/work/config/boost-root/tools/build/src/tools/stage.jam:568: in class(a)installed-exe-generator.__init__ from module object(installed-exe-generator)@4 /home/runner/work/config/boost-root/tools/build/src/kernel/class.jam:90: in new from module class /home/runner/work/config/boost-root/tools/build/src/tools/stage.jam:596: in load from module stage /home/runner/work/config/boost-root/tools/build/src/kernel/modules.jam:295: in import from module modules /home/runner/work/config/boost-root/tools/build/src/tools/builtin.jam:27: in load from module builtin /home/runner/work/config/boost-root/tools/build/src/kernel/modules.jam:295: in import from module modules /home/runner/work/config/boost-root/tools/build/src/build-system.jam:12: in load from module build-system /home/runner/work/config/boost-root/tools/build/src/kernel/modules.jam:295: in import from module modules /home/runner/work/config/boost-root/tools/build/src/kernel/bootstrap.jam:139: in boost-build from module /home/runner/work/config/boost-root/boost-build.jam:17: in module scope from module This is while running ./b2 headers. The initialization/setup code is the same for each architecture as they're run in a GHA matrix so I don't think I've goofed in the CI script. Anyone any ideas what might cause this? Many thanks, John. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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New Boost.Build regression/failure
by John Maddock 08 Feb '21

08 Feb '21

This: https://ci.appveyor.com/project/jzmaddock/config/builds/37592647/job/l6ogy7… Has just started failing. Any ideas anyone? Thanks, John. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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[Flyweight] Hidden symbol visibility
by Deniz Bahadir 08 Feb '21

08 Feb '21

Hi there, I recently made some interesting observation regarding Boost.Flyweight and (hidden) symbol visibility and have now some questions regarding this. Background story: ----------------- In our company's code base we have been using Boost.Flyweight for several years now, compiling it with GCC (and Clang) and it worked just fine. (Thanks for it!) However, lately we are trying to apply hidden symbol visibility to our code base and some of our unit-tests started failing mysteriously. After some intensive investigation I found out that it seems to be due to how we used Boost.Flyweight. We are instantiating it with some custom types, using the default `boost::flyweights::static_holder` class, and are compiling it into a shared library A. However, these Boost.Flyweight types are not only used within that shared library A but also in some other shared library B and in some unit-test executables which link against shared library A. (And these unit-tests started failing.) Observations: ------------- Reading the documentation of Boost.Flyweight and looking at the header `boost/flyweight/static_holder.hpp` I realized that we should have used `boost::flyweights::intermodule_holder` in the first place instead of `boost::flyweights::static_holder`, because we were using Boost.Flyweight from different shared libraries. Still, with non-hidden visibility applied everything always worked correctly even when using `boost::flyweights::static_holder`. Looking at the generated symbols in the different shared libraries I realized that these `static_holder` class types were marked as "unique global symbol" (an GNU extension to the standard set of ELF symbol bindings). So, all shared libraries and executables still used the same single instance of that `static_holder` class (which is the reason why everything worked). With hidden symbol visibility applied by default, these symbols are now marked as local symbols (from the BSS section). So, each shared library as well as the executables have their own version of the `static_holder` class types (which would explain why the equality-comparisions between different Boost.Flyweight variables in our unit-tests now started failing). If I understand it correctly, using `boost::flyweights::intermodule_holder` is the right thing to do, in particular with hidden symbol visibility. Questions: ---------- 1. However, apart from longer program startup times, what other disadvantages might it have to use the `intermodule_holder` instead of the `static_holder` (assuming it still would be marked as "unique global symbol")? 2. And if, as it seems, `static_holder` has some advantages in general, would it be possible to (maybe conditionally) mark the `static_holder` (and/or `static_holder_class`) class with `BOOST_SYMBOL_VISIBLE` or something similar to allow using it even with hidden symbol visibility from different shared libraries? - Only applying default visibility to the template instantiations is ignored by GCC (with warning: "type attributes ignored after type is already defined [-Wattributes]"). - Besides, the C++ standard does not allow applying C++ attributes to template instantiations. (There was a proposal for allowing it, wg21.link/p0537, but I do not know what happened to it.) 3. Would you have any other recommendations or suggestions I did not think about? Thanks for any help or opinion, Deniz -- BENOCS GmbH Dipl.-Inform. Deniz Bahadir Reuchlinstr. 10 D 10553 Berlin Germany Phone: +49 - 30 / 577 0004-22 Email: deniz.bahadir(a)benocs.com www.benocs.com Board of Management: Stephan Schroeder, Dr.-Ing. Ingmar Poese Commercial Register: Amtsgericht Bonn HRB 19378

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BinTray is going away....
by Marshall Clow 06 Feb '21

06 Feb '21

My Friday morning email: > Thank you for supporting JFrog through your use of Bintray. We are and continue to be a community-focused company, and in the spirit of transparency we’re giving you advance notice that as of May 2021, we will be sunsetting Bintray. Just a heads up for now. — Marshall

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Wrong class export/visibility setting for shared libs in many Boost libs
by Alexander Grund 02 Feb '21

02 Feb '21

Hi Boost maintainers, TLDR: Check your classes if they use BOOST_*_DECL and change that to BOOST_SYMBOL_VISIBLE In Boost.ProgramOptions I discovered an issue as a user, where I was unable to catch an exception thrown from the shared Boost library in an executable when both are build with hidden visibility. It turns out the exception class was marked with BOOST_PROGRAM_OPTIONS_DECL which evaluates to "visible" when building the DLL but to nothing when using it. This makes the linker (in theory) mark the typeinfo as hidden which means that the class thrown by Boost and the one tried to catch are unrelated. See https://gcc.gnu.org/wiki/Visibility > Symbol visibility is "default" by default but if the linker encounters just one definition with it hidden - just one - that typeinfo symbol becomes permanently hidden (remember the C++ standard's ODR - one definition rule). This is pretty clear that the current approach done by some Boost libraries doesn't/shouldn't work and BOOST_SYMBOL_VISIBLE should be used instead (or BOOST_SYMBOL_IMPORT should expand to BOOST_SYMBOL_VISIBLE. This depends on how MSCV/Win32 platforms handle class visibility as on Win32 BOOST_SYMBOL_VISIBLE expands to nothing. Maybe someone can clarify here.) As another datapoint: https://github.com/boostorg/config/blob/5bcaa933b55dd58797775d87605a6cdef4a… documents BOOST_SYMBOL_VISIBLE as the macro to be used for this. Libraries which are (very likely) affected by this (quick grep) include: Chrono Container Context Contract Coroutine Fiber Filesystem IOStreams JSON Locale MPI ProgramOptions Python Regex Test Thread Timer Seemingly Linux platforms are less strict in actually enforcing this, due to reason unknown to me. See my SO question: https://stackoverflow.com/questions/65951466/why-can-a-thrown-exception-wit… Reason why this went undetected so far are the above (works on some Linux, fails on e.g. OSX) and that user programs may often not be build with hidden visibility AND rely on the exact same typeinfo from the Boost library (most prominent: exceptions, dynamic_cast) Regards, Alex

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Re: [boost] Wrong class export/visibility setting for shared libs in many Boost libs
by Peter Dimov 02 Feb '21

02 Feb '21

E.g. https://godbolt.org/z/vM6Gxd -----Original Message----- From: Peter Dimov Sent: Tuesday, February 02, 2021 17:01 To: boost(a)lists.boost.org Subject: Re: [boost] Wrong class export/visibility setting for shared libs in many Boost libs Niall Douglas wrote: > I seem to be having difficulty communicating this to anyone here, so > here's a godbolt: > > https://godbolt.org/z/jv5Y75 But you've provided a definition for thirdpartylib_nothidden. This is not the case under discussion. The case under discussion is making BOOST_SYMBOL_IMPORT imply _VISIBLE, which translates to a default visibility attribute on the _declaration_ of thirdpartylib_nothidden.

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Google Summer of Code
by Radu Cosma 30 Jan '21

30 Jan '21

Good afternoon, My name is Radu Cosma and I would like to be a contributor to the Boost C++ Libraries in the context of Google Summer of Code 2021 (as a start :) ). I understand that the topics have yet to be posted and that there is a competency test involved. Could you please tell me the relevant information regarding this and the application process? Thank you in advance! Kind regards, Radu Cosma

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What's the reason Boost.Asio tss_ptr doesn't use __declspec(thread) on Windows?
by Groke, Paul 29 Jan '21

29 Jan '21

Hi, I've noticed that Boost.Asio's tss_ptr implementation doesn't use __declspec(thread) on Windows, except when compiling for WinRT. Instead it uses the win_tss_ptr implementation - which will cause a crash when there's no free TLS index. (There are static tss_ptr instances and loading a DLL where a ctor of a static variables throws a C++ exception seems to cause a crash -- no surprise there). AFAIK using implicit TLS via __declspec(thread) should fix this so that loading a DLL either works or fails gracefully. One problem that I know of with implicit TLS is that it fails catastrophically on Windows versions before Vista. Since WinRT wasn't available on pre-Vista versions, this might be a reason to restrict it to WinRT. But I don't know if there are/were other reasons to restrict use of implicit TLS to WinRT. So... is there another reason? If there's no other reason, that would be great, because we don't have to support pre-Vista versions. Meaning we could simply patch Boost.Asio to use implicit TLS for MSVC in general. Regards, Paul Groke

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Have we become too Intel x64 centered?
by John Maddock 28 Jan '21

28 Jan '21

I have no solution for this, but I note that neither do we have CI, nor tests on https://www.boost.org/development/tests/develop/developer/summary.html that aren't Intel x86. The compiler list has shrunk to msvc/clang/gcc as well. I note that at least in theory, other platforms/architectures could be integrated into Drone CI (either the CppAlliance one, or our own), but someone would have to offer to host the clients running the tests. Any thoughts/solutions? Cheers, John. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

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Introduction
by Aman Verma 28 Jan '21

28 Jan '21

Hello Boost C++ Community, I am Aman from Indian Institute of technology Kanpur and currently, I am pursuing my bachelor's in Electrical engineering. I have 3 years of experience in C++. I am extremely eager and excited about contributing to various projects of Boost C++. I am willing to participate in GSOC'21 with Boost C++. I have gone through the project proposals and I find myself interested in the following projects: 1. ublas 2. Multiprecision 3. Geometry I would great if I could connect with the respective mentors and move onto further steps. Regards Aman

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