May 2020 - Boost-users - lists.boost.org

Boost.Numeric.Interval: Please specify rounding control mechanism
by Bastien Commelongue 01 Dec '20

01 Dec '20

Hello, I am building an app for IOS (ARM) and I had this issue while compiling: *Boost.Numeric.Interval: Please specify rounding control mechanism.* C99 version should be used in this case but __USE_ISOC99 is not defined. Modifying the condition with this code (using __cplusplus) fixed the issue: *boost/numeric/interval/hw_rounding.hpp(36)* *#if defined(BOOST_NUMERIC_INTERVAL_NO_HARDWARE) && (defined(__USE_ISOC99) || defined(__MSL__) || (defined __cplusplus && __cplusplus >= 201103L))# include <boost/numeric/interval/detail/c99_rounding_control.hpp>#endif* Let me know if I missed something or if you plan to integrate this modification in a next version. Cheers, Bastien Commelongue

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[review][LEAF] Review of LEAF starts today : May 22 - May 31
by Michael Caisse 02 Jun '20

02 Jun '20

The Boost formal review of Emil Dotchevski's LEAF (Lightweight Error Augmentation Framework) library will take place from May 22 through May 31st. LEAF isn't just another error reporting library in the family of expected-like types. It provides a unique take on error handling which plays into usability, flexibility, and performance. Every software developer must deal with handling errors which makes this review relevant to all. Please participate! I will be grateful to receive a review based on whatever level of effort or time you can devote. LEAF is brought to us by Emil Dotchevski, the author of Boost.Exception. Similar to Boost.Exception, this library allows arbitrary error objects to be returned; however, unlike Boost.Exception it does not require dynamic memory. The library can be used with or without exception handling. The LEAF documentation highlights the following features: * Efficient delivery of arbitrary error objects to the correct error handling scope. * No dynamic memory allocations. * Compatible with std::error_code, errno and any other error code type. * Can be used with or without exception handling. * Support for multi-thread programming. "LEAF is designed with a strong bias towards the common use case where callers of functions which may fail check for success and forward errors up the call chain but do not handle them." LEAF offers a pattern matching facility to specify which errors to handle and how to handle them. Take a look at the 5-minute Introduction. <https://zajo.github.io/leaf/#introduction> You can find the source code to be reviewed here: <https://github.com/zajo/leaf/tree/review> You can find the documentation here: <https://zajo.github.io/leaf/> The documentation includes a tutorial, examples, reference, design rationale, and comparisons to other error handling approaches/libraries. There is a benchmark document also: <https://github.com/zajo/leaf/blob/master/benchmark/benchmark.md> and a whitepaper: <https://github.com/zajo/leaf/blob/master/doc/whitepaper.md> Please provide in your review information you think is valuable to understand your choice to ACCEPT or REJECT including LEAF 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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[review][LEAF] Review of LEAF
by Sorin Fetche 01 Jun '20

01 Jun '20

On Fri, May 22, 2020 at 2:37 AM Michael Caisse via Boost <boost(a)lists.boost.org> wrote: > > The Boost formal review of Emil Dotchevski's LEAF (Lightweight Error > Augmentation Framework) library will take place from May 22 through May > 31st. I wholeheartedly recommend ACCEPTing LEAF as a Boost library I base my recommendation on both the qualities of the library itself and the responsiveness and openness for feedback of its author. As a background, more than year ago, I evaluated error handling using LEAF in the context of an in-house support library for implementing C++ RESTful services. I consider the error handling for microservices based architectures very important because it needs to cover two, sometimes competing, requirements: - as debug logs are less than ideal in distributed systems, an error condition should capture and carry with it as much context and debug information as possible as it propagates back across the stack (both in-process and across different processes/services); - the end-user of the system should not just get a dump of meaningless debug information when an error condition occurred (but neither just a generic "internal error occurred" one). And, coming from the experience of using Boost.Exception for an earlier version of such a utility library, LEAF seemed a very good candidate. So, as part of this evaluation, I tried to see how it would fit alongside Boost.Asio and Boost.Beast in building this REST oriented scaffolding. Through the course of this experimentation, LEAF improved its support for being used with Asio style asynchronous operations and multi-threading. It also includes now an example built at that time that showcases a possible way for how this integration can be be achieved. > - What is your evaluation of the design? Excellent as it allows bridging multiple error handling strategies and usage patterns in an efficient way. I view it as a clear successor to Boost.Exception and has very good interoperability with Boost.Outcome. > - What is your evaluation of the implementation? I have not studied it in depth but from what I can tell, as a user of the library, it is very solid. > - What is your evaluation of the documentation? Excellent! > - What is your evaluation of the potential usefulness of the library? It might not cover any possible usage scenario with error reporting and handling being such a generic problem space that often has conflicting requirements, but for sure it covers enough of it to warrant its inclusion in Boost. > - Did you try to use the library? With which compiler(s)? Did you > have any problems? Yes, extensively last year. Less so, recently [*] Tried it with Visual Studio 2019, g++ 7.3 and 8.2, clang 7.0 > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? In depth study and usage about an year ago. Following the changes it has suffered since then (nothing significant from what I can tell). > - Are you knowledgeable about the problem domain? > I have used multiple error handling libraries over time. And, I also had to deal with distributed systems that had an improper or lacking error handling design, something simply slapped on as an afterthought. [*] The part of the project requiring C++ based services and by extension the infrastructure to enable writing them has been postponed as we (the team I'm part of) focused more on the environment where these services would run. I expect we'll resume this work sometime later this year. And at that time we'll start using the LEAF library again. Best regards, Sorin Fetche

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[review][LEAF] Review period ending soon - May 31
by Michael Caisse 30 May '20

30 May '20

I'd like to encourage each of you to review Emil's error handling library. We often focus on design or implementation based reviews, and I encourage those but what I would really like to see are more user based reviews. Grab the library and docs and play with it a bit. What works well? What can be improved? As a reminder, some of LEAF's features include: * arbitrary error types * header-only * no dependencies * use without exceptions * use with exceptions * no dynamic memory alloc You can find the documentation here: <https://zajo.github.io/leaf/> and the library source here: <https://github.com/zajo/leaf/tree/review> Thanks! michael -- Michael Caisse Ciere Consulting ciere.com

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installing boost in mac
by RUIZ PUJADAS, Esmeralda 30 May '20

30 May '20

Hello, I wanted to install the version 1.67 in mac as i have it in windows (the newest version 1.73 is not working for me) but i read that it is not compatible with mac. The version compatible with mac is above 1.69. So i decided to install this one. If I am mistaken let me know. I wanted to ask you if it is normal to get 524 warnings. All the warnings say the same: warning: empty macro arguments are a C99 feature [-Wc99-extensions] I just did it like this FrankGrimes:Desktop user$ cd boost_1_69_0 FrankGrimes:boost_1_69_0 user$ ./bootstrap.sh --prefix=/Users/user/boost FrankGrimes:boost_1_69_0 user$ ./b2 install Thise warnings will have any influence with my code. I am using xcode and I am having errors with boost due to unused parameters in args in filter_parser.hpp functions so i do not know if this error has something to do with it. Thanks

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[Boost.Graph] Custom vertex properties with std::shared_ptr member ?
by Nicholas Yue 25 May '20

25 May '20

Hi, struct CustomVertex { std::string name; std::shared_ptr<AbstractNodeClass> _node; }; typedef boost::adjacency_list < boost::vecS, boost::vecS, boost::bidirectionalS, CustomVertex> Graph; Vertex DGManager::createVertex(const std::string &name, std::shared_ptr<AbstractNodeClass> Ptr) { _activeVertex = boost::add_vertex(CustomVertex{name, nodePtr}, _g); return _activeVertex; } With Visual Studio 2017, the above is fine but with GCC 7.5.0, I get a seg-fault on application exit. Looking at the stack trace, it looks like a problem in the CustomVertex destructor. Is there some restriction as to what types we can use as member variable of Custom Vertex Properties ? Kind regards -- Nicholas Yue Graphics - Arnold, Alembic, RenderMan, OpenGL, HDF5 Custom Dev - C++ porting, OSX, Linux, Windows http://au.linkedin.com/in/nicholasyue https://vimeo.com/channels/naiadtools

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boost build from source code
by Leonid Meyerovich 21 May '20

21 May '20

Hello, bootstrao.sh file on Linux machine create b2 executable (copy it on boost root directory) cd "$pwd" BJAM="$my_dir/tools/build/src/engine/b2" echo "tools/build/src/engine/b2" cp "$BJAM" . Running b2 shows the error ./b2 bash: ./b2: cannot execute binary file: Exec format error Can somebody explain? Thank you, Leonid ________________________________ This message and all attachments are PRIVATE, and contain information that is PROPRIETARY to Intelligent Automation, Inc. You are not authorized to transmit or otherwise disclose this message or any attachments to any third party whatsoever without the express written consent of Intelligent Automation, Inc. If you received this message in error or you are not willing to view this message or any attachments on a confidential basis, please immediately delete this email and any attachments and notify Intelligent Automation, Inc.

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Review Wizard Status Report for May 2020
by Mateusz Loskot 20 May '20

20 May '20

============================================== Review Wizard Status Report for May 2020 ============================================== News ==== List of events that happened since the last report in 2016 is long and includes 13 releases of Boost, 21 libraries accepted and 4 libraries rejected. Details at https://www.boost.org/community/review_schedule.html What happened in 2020: 1. 2020-01: Ronald Garcia retired as a Review Wizard. Thank you Ronald! 2. 2020-02: StaticString accepted 3. 2020-04: Boost 1.73 Released New Libraries: - Nowide from Artyom Beilis, maintained by Alexander Grund - StaticString from Vinnie Falco and Krystian Stasiowski 4. 2020-05: Bimap library needs a maintainer https://lists.boost.org/Archives/boost/2020/05/248940.php Review Schedule Status ====================== The following libraries need a review manager: * JSON - author: Vinnie Falco, Krystian Stasiowski, Peter Dimov The following libraries have review managers, but have not yet been scheduled for review: * none The following libraries have review managers and have been scheduled for review: * LEAF - May 22, 2020 - May 31, 2020; author: Emil Dotchevski; review manager: Michael Caisse * Text - June 11, 2020 - June 20, 2020; author: Zach Laine; review manager: Glen Fernandes The following libraries have been reviewed and await reports from their review managers: * none The following libraries have been accepted to Boost, but have not yet been integrated into Boost Git: * Double-Ended - conditionally accepted in October 2017; author: Benedek Thaler * Parallel Sorting Sub-library - accepted November 2016; author: Francisco José Tapia The following libraries have been accepted and submitted to Boost Git, but have not yet appeared in a release: * STLInterfaces - conditionally accepted December 2019; author: Zach Laine The following libraries have been accepted provisionally to Boost, but have not been submitted for mini-review and full acceptance: * STLInterfaces - conditionally accepted December 2019; author: Zach Laine General Announcements ===================== As always, we need experienced review managers. Please take a look at the list of libraries in need of managers and check out their descriptions. In general review managers are active boost participants, including library contributors, infrastructure contributors, and other mailing list participants with a substantial track record of constructive participation. If you can serve as review manager for any of them, email us at Mateusz Loskot (mateusz at loskot dot net) or John Phillips (johnphillipsithaca at gmail dot com). We are also suffering from a lack of reviewers. While we all understand time pressures and the need to complete paying work, the strength of Boost is based on the detailed and informed reviews submitted by you. If you are interested in reviewing a library but won't have time during the review period, you can always prepare your review ahead of time. No rule says you can only work on a review during the review period. A link to this report will be posted to www.boost.org. If you would like us to make any modifications or additions to this report, please email Mateusz. The review schedule is an unordered list of the libraries awaiting review. As such, any library on the schedule can be reviewed once the developer is ready, a review manager has been secured, and the manager, developer, and wizards agree on a date to schedule the review. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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ubuntu cross-compile boost library for ARM
by Leonid Meyerovich 19 May '20

19 May '20

Hello Everyone, I have spent some time trying to build BOOST libraries from source code on Ubuntu machine. BOOST version is boost_1_73_0. I use ARM compiler echo $CC arm-oe-linux-gnueabi-gcc -march=armv7-a -mfloat-abi=hard -mfpu=neon --sysroot=/home/lm/rfnoc/oe/sysroots/armv7ahf-vfp-neon-oe-linux-gnueabi My current directory is boost_1_73_0 1. I have edited user-config.jam file, adding gcc_root = $(CC) ; using gcc : arm : $(gcc_root) This file is located on 'parent' BOOST directory - boost_1_73_0. 2. Run lm@ubuntu:~/boost/boost_1_73_0$ ./bootstrap.sh --prefix=bbb Building Boost.Build engine with toolset gcc... tools/build/src/engine/b2 Detecting Python version... 2.7 Detecting Python root... /home/lm/rfnoc/oe/sysroots/x86_64-oesdk-linux/usr Unicode/ICU support for Boost.Regex?... /usr Backing up existing Boost.Build configuration in project-config.jam.4 Generating Boost.Build configuration in project-config.jam for gcc... 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://www.boost.org/more/getting_started/unix-variants.html - Boost.Build documentation: http://www.boost.org/build/ 3. So far it looks OK, I run b2 and have got an error lm@ubuntu:~ /boost/boost_1_73_0$ b2 /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/tools/features/warnings-feature.jam:27: in load ERROR: rule "[[bbv2.builtin.features.warnings]]`warnings`::" unknown in module "warnings-feature". /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/kernel/modules.jam:295: in import /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/tools/features/__init_features__.jam:22: in load /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/kernel/modules.jam:295: in import /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/tools/builtin.jam:16: in load /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/kernel/modules.jam:295: in import /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/build-system.jam:12: in load /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/kernel/modules.jam:295: in import /home/lm/covra-liquidsdr/boost/boost_1_73_0/tools/build/src/kernel/bootstrap.jam:139: in boost-build /home/lm/covra-liquidsdr/boost/boost_1_73_0/boost-build.jam:17: in module scope Could somebody explain what this error means and what I am doing wrong? Thank you, Leonid ________________________________ This message and all attachments are PRIVATE, and contain information that is PROPRIETARY to Intelligent Automation, Inc. You are not authorized to transmit or otherwise disclose this message or any attachments to any third party whatsoever without the express written consent of Intelligent Automation, Inc. If you received this message in error or you are not willing to view this message or any attachments on a confidential basis, please immediately delete this email and any attachments and notify Intelligent Automation, Inc.

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BoostDLL : Multiple plugins in a single *.so/*.dll file
by Nicholas Yue 18 May '20

18 May '20

Hi, I am currently able to load each plugin in a given shared library. i.e. one plugin for each corresponding *.so/*.dll file However, as the number of plugins increases, I am wondering if there is a way to structure my plugins so that it all resides in a single *.so/*.dll file Additionally, how should one create the individual plugins in a single *.so/*.dll to be able to call their static method ? I have not found such examples so I am not sure if I am using the wrong search terms or it is currently not supported by design in BoostDLL. Cheers -- Nicholas Yue Graphics - Arnold, Alembic, RenderMan, OpenGL, HDF5 Custom Dev - C++ porting, OSX, Linux, Windows http://au.linkedin.com/in/nicholasyue https://vimeo.com/channels/naiadtools

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[Multiprecision] number conversion to __int128
by A.Dmitrovsky 18 May '20

18 May '20

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[Boost.Test] Three-way comparison operator
by Leo Carreon 17 May '20

17 May '20

Hi Boosters, Does anyone know if Boost.Test has been updated to provide support for the three-way comparison operator? I’m asking because I’ve encountered a situation where my user-defined class provides the three-way comparison operator but when I perform comparisons using Boost.Test it complains that my class has no ‘operator==’ which is true because it provides ‘operator<=>’. Please note that I’m using Boost 1.73.0 and g++ 10.0.1. Is there any plan to add the three-way comparison operator support? Kind regards, Leo

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warning C4275, C4271when using boost::noncopyable
by Roman Savchenko 14 May '20

14 May '20

Hi All, I'm trying to update from boost 1.62 to boost 1.73. Boost 1.62 was built with VS15 140 toolchain with shared runtime (/MD) and as static lib. Boost 1.73 was built with VS19 140 toolchain with /MD and as static lib. I have a class: #include <boost/noncopyable.h> class __declspec(dllexport) A : private boost::noncopyable when I'm using 1.62 I do not have such warning. when I'm using 1.73 I do have such warning. I'll appreciate if anyone could help me to understand what I'm missing. Why does new version of header generate this warning? Thanks, Roman

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(no subject)
by Ritajit Kundu 10 May '20

10 May '20

I am trying to compute a 2 Dimensional numerical integration with the help of Boost. I've been reading the documentation for a couple of days and my CPP language knowledge is just up to legacy CPP level so I'm a noob. I saw this page <https://www.boost.org/doc/libs/1_73_0/libs/math/doc/html/math_toolkit/gauss…> in documentation which calculates the quadrature using* Gauss-Kronrod *rule. I was trying to build upon it and calculate a 2-d integral using Gauss-Kronrod rule. My understanding is *a 2D integral is basically 2 1D integrals with the Cartesian product.* So I was thinking If I can nest two integration function then I'm done. I've started from the aforementioned example and extended it a bit so the code for a 2d integration looks like, #include <boost/math/quadrature/gauss_kronrod.hpp> #include <iostream> int main(int argc, char *argv[]) { using namespace boost::math::quadrature; auto f1 = [](double t, double s) { return std::exp(-(t*t+s*s+t*s) / 2); }; double error; double Q = gauss_kronrod<double, 15>::integrate(gauss_kronrod<double, 61>::integrate(f1, 0, std::numeric_limits<double>::infinity(), 5), 0, std::numeric_limits<double>::infinity(), 5, 1e-9, &error); std::cout << Q << " " << error<<std::endl; return 0; } . I've just added a lambda function (which is the integrand) of two variables and nested 2 1D Gauss-Kronrod integration functions. I'm compiling this with g++ -Wall -I /path/to/boost_1_73_0 2d-gauss.cpp This gives error and compilation fails. I don't know what wrong I'm doing. How do you suggest to do such an integral? Thanks in advance.

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Google Summer of Code 2020 selected projects
by David Bellot 09 May '20

09 May '20

Dear Boost community, I would like to welcome our Google Summer of Code. 2020 students. This year, 10 students will work very very hard on improving and adding new features to many of our libraries. Once again, the competition has been very hard. A few numbers: - we received 93 proposals in total. 85 of them were complete, then we kept 47 proposals only - finally we selected 10 of them, covering 7 different Boost libraries - and countless hours of work from the most incredible team of mentors! Here are the list of projects for 2020: *Boost.Real* Kishan Shukla will be working on making the Real library ready for revision. His main goal is to reimplement the division algorithm so it can be used with any number base representation and the Karatsuba multiplication algorithm. Also, it will be working on implementing some operators and common irratianal numbers as Pi. Mentors: Laouen Belloli and Damian Vicino. *Boost.Astronomy* Syed Ali Hasan will be working on the astronomical coordinate system, he will implement different coordinate conversion using SOFA library Mentor: Pranam Lashkari Gopi Krishna Menon will be completing the parser for FITS file and also optimise the already developed components. Mentor: Sarthak Singhal *Boost.GIL* Debabrata Mandal will be implementing histogram computation as a built-in feature, algorithms for histogram analysis, image processing algorithms based on histogram and possibly integration with Boost.Histogram library. *Mentor*: Mateusz Loskot, Pranam Lashkari Olzhas Zhumabek will be extending GIL's portfolio of image processing algorithms, implementing for image scaling and sampling, Perona–Malik diffusion, Non-Maximum Suppression for object detection, Hysteresis threshold and some more. *Mentor*: Mateusz Loskot *Boost.Multiprecision* Dimitris Los will work on extending and optimizing parts of Boost.Multiprecision to higher precision of many thousands of bits or more. *Mentor*: Christopher Kormanyos *Boost.uBlas* Ashar Khan will stabilize and improve Boost.uBlas using the C++20-Standard. The main focus of his project will be enhancing code-coverage and documentation, integrating static code analysis and generating tensor concepts. *Mentor*: Cem Bassoy Tom Kwok will improve and finalize the implementation of data frames in uBlas, with the aim of delivering production-ready by the end of the summer. Data frame in uBlas are similar in functionalities to other implementations like in R, Python.Pandas or Julia. *Mentor*: David Bellot *Boost.Geometry* Tinko Bartels will work on robust yet efficient geometric predicates for Boost Geometry. *Mentor*: Vissarion Fisikopoulos *Boost.Real* Vikram Singh Chundawat will work in taking Real to revision ready state. His focus will be in improving the internal representation datatypes and providing functions required to conveniently support Taylor series. *Mentors*: Damian Vicino and Laouen Belloli Best regards, David Bellot

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boost::filesystem::perms on Windows
by Dominique Devienne 07 May '20

07 May '20

Hi. I'm not having any luck with finding out whether a folder is writable or not, on Windows. Is Boost.Filesystem (1.64) supposed to work on Windows for permissions? Especially in "special" folders like those in "C:\Program Files"? C:\Program Files\Vendor\App>echo foo > bar Access is denied. But Boost.Filesystem reports permissions as rw-rw-rw-, when printing them using the BFS-equivalent to the example available on CppReference https://en.cppreference.com/w/cpp/filesystem/perms Despite obviously the folder not being writable, w/o being an administrator. I'm naively using simple code like below: ``` fs::path path(name); fs::file_status stat = fs::status(path); fs::perms p = stat.permissions(); demo_perms(p); ``` Am I missing something obvious? Thanks, --DD PS: I worked around the above, actually trying to create a file, but that has corner cases too, and I'd much prefer a reliable and cross-platform .permissions() from Boost. Smoothing-over platform differences is one "raison d'etre" from Boost after all, no?

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Fwd: [serialization] is the weak_ptr parent kept inside an iarchive
by ypotin 05 May '20

05 May '20

Hello, I was running some tests involving std::weak_ptr using boost serialization, and I realized that when I read a std::weak_ptr from an archive that doesn't contain the "parent" std::share_ptr, the behavior of the read pointer is "hard to understand". Here is an example : #include <cassert> #include <sstream> #include <memory> #include <boost/archive/binary_iarchive.hpp> #include <boost/archive/binary_oarchive.hpp> #include <boost/serialization/export.hpp> #include <boost/serialization/shared_ptr.hpp> #include <boost/serialization/weak_ptr.hpp> class MyInt { public: MyInt() : value(0) { } int value; template<class Archive> void serialize(Archive &ar, unsigned int) { ar & value; } }; int main() { std::stringstream data; { std::shared_ptr<MyInt> shared = std::make_shared<MyInt>(); assert(shared.use_count() == 1); shared->value = 12; /* Write a weak_ptr */ { std::weak_ptr<MyInt> weak(shared); assert(shared.use_count() == 1); boost::archive::binary_oarchive ar(data); ar << weak; assert(shared.use_count() == 1); } assert(shared.use_count() == 1); /* Read a weak_ptr */ std::weak_ptr<MyInt> weak; { boost::archive::binary_iarchive ar(data); ar >> weak; assert(shared.use_count() == 1); assert(weak.use_count() == 1); { std::shared_ptr<MyInt> loaded = weak.lock(); assert(loaded); /* It looks good */ assert(loaded->value == 12); /* Let's see... */ assert(loaded != shared); shared->value = 42; assert(loaded->value == 12); /* So another shared_ptr exists somewhere... */ assert(shared.use_count() == 1); assert(loaded.use_count() == 2); assert(weak.use_count() == 2); } /* But where ? */ assert(shared.use_count() == 1); assert(weak.use_count() == 1); } /* Let's see */ assert(shared.use_count() == 1); assert(weak.use_count() == 0 /* weak.expired() */); /* Hmm, was it inside the archive itself ? */ } /* Let's try again, we need the input stream to be back to the beginning */ data.seekg(0); std::weak_ptr<MyInt> weak; { boost::archive::binary_iarchive ar(data); assert(weak.use_count() == 0); ar >> weak; assert(weak.use_count() == 1); /* It looks fine */ } assert(weak.use_count() == 0); /* aw, on a second thought, it really doesn't */ return 0; } I am building and running this using g++-9.3.0 with boost-1.72.0-1. Clearly, the weak_ptr gets itself a shared_ptr "somewhere" as it can be used after being read. I was wondering "where it is stored and how to access it, if possible, without some `weak.lock()` call ?" It looks like the shared_ptr gets destroyed at the same time as the archive, so I guess it is cleaned up thanks to the delete_created_pointers method when the iarchive is destroyed : does delete_created_pointers actually contains also shared_ptr ? As far as I can see in the code serialization/weak_ptr.hpp, we actually save then load a std::shared_ptr, so I was expecting the weak_ptr to expire as soon as the call returns : since it is not, there *is* another reference. Now, I know I must save the shared_ptr in the archive myself to have my own reference and to get all weak_ptr running properly. But I came across this use case and I can't take it out of my mind, so if you have an explanation, I'm all ears. Thank you

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Boost 1.73, beast and -fconcepts
by David P. Riedel 03 May '20

03 May '20

Hi It seems that beast still does not work with gcc 9.3 and -fconcepts. If I try to build the beast test programs using -fconcepts, I still get a lot of errors such as those below. I thought this was fixed in 1.73. ???? Thanks --------------------- In file included from ../../../boost/beast/core/basic_stream.hpp:1457, from ../../../boost/beast/core.hpp:16, from doc/core_snippets.cpp:19: ../../../boost/beast/core/impl/basic_stream.hpp:781:1: error: no declaration matches ‘auto boost::beast::basic_stream< <template-parameter-1-1>, <template-parameter-1-2>, <template-parameter-1-3> >::async_connect(const endpoint_type&, ConnectHandler&&)’ 781 | basic_stream<Protocol, Executor, RatePolicy>:: | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from ../../../boost/beast/core.hpp:16, from doc/core_snippets.cpp:19: ../../../boost/beast/core/basic_stream.hpp:1202:5: note: candidates are: ‘template<class Protocol, class Executor, class RatePolicy> template<class Iterator, class ConnectCondition, class IteratorConnectHandler> requires completion_token_for<IteratorConnectHandler, void()> typename boost::asio::async_result<typename std::decay<RangeConnectHandler>::type, void(boost::system::error_code, Iterator)>::return_type boost::beast::basic_stream< <template-parameter-1-1>, <template-parameter-1-2>, <template-parameter-1-3> >::async_connect(Iterator, Iterator, ConnectCondition, IteratorConnectHandler&&)’ 1202 | async_connect( | ^~~~~~~~~~~~~ ../../../boost/beast/core/basic_stream.hpp:1141:5: note: ‘template<class Protocol, class Executor, class RatePolicy> template<class Iterator, class IteratorConnectHandler> requires completion_token_for<IteratorConnectHandler, void()> typename boost::asio::async_result<typename std::decay<RangeConnectHandler>::type, void(boost::system::error_code, Iterator)>::return_type boost::beast::basic_stream< <template-parameter-1-1>, <template-parameter-1-2>, <template-parameter-1-3> >::async_connect(Iterator, Iterator, IteratorCon

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[review] [LEAF] LEAF Review Starts May 22
by Michael Caisse 30 Apr '20

30 Apr '20

The Boost formal review for LEAF (Lightweight Error Augmentation Framework) will take place May 22, 2020 through May 31st. LEAF is brought to us by Emil Dotchevski, the author of Boost.Exception. Similar to Boost.Exception, this library allows arbitrary error objects to be returned; however, unlike Boost.Exception it does not require dynamic memory. The library can be used with or without exception handling. Error handling is such an import part of every software system. LEAF provides a unique solution to the problem. The excellent documentation can be found here: <https://zajo.github.io/leaf/> and includes a tutorial, examples, reference, design rationale, and comparisons to other error handling approaches/libraries. The source is available at github. The review branch will be used during the review period. <https://github.com/zajo/leaf/tree/review> The purpose of this announcement is to give people some time to start looking at the documentation and source code for the library. Feel free to begin asking questions. Most of all, get involved! Everybody has some experience with handling errors. Tell the Boost community what you think of LEAF. Thank you for your participation! michael -- Michael Caisse Ciere Consulting ciere.com

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