May 2018 - Boost - lists.preview.boost.org

[RFC] unique_val (handles, IDs, descriptors...)
by Miguel Ojeda 15 Oct '18

15 Oct '18

Hi all, While working on a medium-sized project, I had to wrap quite some handles, IDs, descriptors, etc. into RAII classes. Somehow, writing those and making them movable seemed more verbose than needed. I searched in the STL and Boost for something already implemented, but nothing seemed to come up. I decided to write my own prototype to see whether I was missing something important; but actually using it in my project felt quite natural and simple. At this point, I asked for a second opinion from a well-known expert (thanks Scott!) and he agreed that it seemed like a reasonable idea but, of course, he would also be surprised if others haven't come up with something similar. So I polished it up a bit and uploaded it to: https://github.com/ojeda/unique_val Below you have the introduction inlined [1]. If you have the time, please take a look (specially to the Rationale) and let me know your comments. The code itself is very short and straightforward. If you already have this class/template in Boost somewhere that I missed, please let me know! Otherwise, if you think this could be interesting to put into Boost in some existing library (not sure which) or as a new tiny library, I would be glad to make the effort to expand it, clean it up, etc. Thank you! Miguel [1] """ A single-header header-only library for representing unique values (handles, IDs, descriptors...) that default to a value on move for C++11, C++14 and C++17. It simplifies writing resource-owning classes (RAII) with move semantics support for resources with handles, IDs or descriptors that are supposed to be used as unique values, not as unique pointers. For instance, it can be used with non-pointer handlers (like the `int` file/socket descriptors in POSIX) and with opaque pointer handlers (like the `HWND` handles in the Win32 API). As such, it can be used as an alternative to `std::unique_ptr` with or without custom deleter, specially for resources that use a non-pointer type or resources that are not simply heap-allocated. It does not have any overhead compared to using the original type. It supports booleans, integers, pointers and enumerations. The default value can be different than the default-constructed value (i.e. different than 0, nullptr, etc.). """

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Original STL Library Documentation has been recovered and is now safe forever.
by Robert Ramey 02 Sep '18

02 Sep '18

The Standard Template Library is the foundation of modern C++. The creation and publication of this code and its documentation set a new standard for the formal specification of what a computer program should do, how it should be designed and how it should be formally documented. These pages were maintained first by Silicon Graphics and then later by Hewett-Packard. In January of 2018 these pages were removed by H-P. This is a historic blunder. I have recovered the original STL Library Document and hosted them here: http://www.rrsd.com/software_development/stl/index.htm Robert Ramey

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Docker environment(s) for Boost Development
by James E. King, III 26 Jul '18

26 Jul '18

I submitted a pull request into the superproject containing some docker scripts. The intention of this is to simplify managing a docker build environment for boost: https://github.com/boostorg/boost/pull/184 I'm wondering if folks will find this useful, and whether folks think this should be in its own submodule instead of being in boostorg/boost. I only have an Ubuntu Bionic environment in this pull request but it wouldn't be that difficult to add debian, centos, and others, as well as various versions of each. I have tested it on Unix and on Windows. On Unix the performance is quite good overall - but on Windows since they use SMB to do the sharing it is really slow (I would say a good 20 times slower between typing "b2" and getting the first output as it scans through all the files. I would recommend continuing to use a virtual machine on Windows Hosts for unix boost development, but this option is there and hopefully they will improve things. This partially came out of the discussion we had a number of months back about how we handle third party dependencies. For the most part one has to look at README files in various locations to learn about them. This is an attempt to pull all the dependencies together for a complete build into one place (the Dockerfile). One day when Microsoft supports Visual Studio compilation inside a reasonably sized windows container (i.e. based on nanoserver and not Windows Server Core), I'd like to add that as well since managing the dependencies on Windows is a bit harder (you usually have to build them). Thanks, Jim

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Boost.Signals deprecation and removal
by James E. King, III 15 Jul '18

15 Jul '18

This first implementation of signals has been deprecated since the 1.54 release. (When) are we going to remove it? It is under management of the CMT, and it has been deprecated for over 10 major releases. I would like to suggest we remove it in the Boost 1.68.0 release. - Jim

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[Build] Create test with shared library linked against current Boost link-variant
by Alexander Grund 18 Jun '18

18 Jun '18

Hi, I discovered a severe bug in Boost.Serialization and am trying to contribute a test to the test suite to reproduce that behavior. I have a minimum example which runs into this (see also https://stackoverflow.com/questions/50064617/order-of-destruction-for-stati…) but I'm having trouble getting that into the Jamfile. What I need: 2 shared libraries linked against the currently tested Boost link-variant and link those into an executable not linked against Boost. So testcase a) would be against Boost-Shared and b) against Boost-Static. But in all cases the libraries itself must be shared. What I have: lib multi_shared_1 : multi_shared1.cpp ../build//boost_serialization : <link>shared ; lib multi_shared_2 : multi_shared2.cpp ../build//boost_serialization : <link>shared ; ... [ test-bsl-run test_multi_shared_lib : : multi_shared_1 multi_shared_2 ] Problem: This links against Boost-Shared even with "./b2 link=static" My best approach so far is to change "../build//boost_serialization" to "../build//boost_serialization/<link>static" but then I cannot test testcase a) (Boost-Shared) anymore. Also it does link other Boost-Libraries (filesystem, system) shared, not static. Furthermore I'd need to add `-fPIC` to the cxxflags of the boost libraries. This is minor as it can be done in the `.travis` file but I'd rather have it in the Jamfile so it is not missed in other test-environments. How can I achieve this? I'm not to familiar with the Jamfiles so this is basically all I could find so far. Thanks, Alexander Grund

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[outcome] v2.1 progress report
by Niall Douglas 04 Jun '18

04 Jun '18

Dear Boost, Two months after you accepted Outcome into Boost, I am pleased to say that I believe that all the known bugs and very substantial source refactoring recommended by the peer review have been implemented (detailed changelog is appended below). What remains is a few months of maturing in real world use as all this severe refactoring needs to be tested outside a test suite, and of course the documentation which I don't intend to start work on until the autumn. The Boost edition has, obviously, received a major upgrade and it is now 100% "Boost native" in that it uses Boost.System and Boost.Exception now. The test suite for the Boost edition exclusively tests the Boost native edition, and it all passes. Outcome (both standalone and Boost editions) now can handle both Boost and std types freely intermixed as you see fit. A new "lite" single header edition exists which drags in virtually no system headers, and is hideously low impact on compile times as a result. ABI and API stability have been dumped to git repo with scripting to check the current library against the frozen dumps. This edition should make the corporate crowd very pleased. Very little should appear to have changed from the outside. Code written for v2.0 ought to, more or less, compile and work as before with v2.1. I would appreciate whatever help the Boost community can give in helping to test this edition. I expect new bugs to have been introduced given the severe source code refactoring, and new dual support for Boost and std as equals. My gratitude in advance. Niall --- ## v2.1 in progress [[project]](https://github.com/ned14/outcome/projects/1) - Boost edition is now 100% Boost, so defaults for `result` and `outcome` are `boost::system::error_code::errc_t` and `boost::exception_ptr`. Moreover, the test suite in the Boost edition now exclusively tests the Boost edition. One can, of course, freely use the standalone edition with Boost, and the Boost edition with `std` types. - Renamed ADL discovered customisation point `throw_as_system_error_with_payload()` to `outcome_throw_as_system_error_with_payload()`. - [#135](https://github.com/ned14/outcome/issues/135) - Added much clearer compile failure when user tries `result<T, T>` or `outcome` where two or more types are identical. Thanks to Andrzej Krzemieński for suggesting a technique which combines SFINAE correctness with the remaining ability for `result<T, T>` etc to be a valid type, but not constructible. - [#67](https://github.com/ned14/outcome/issues/67) - Fixed one of the oldest long open bugs in Outcome, that the noexcept unit tests failed on OS X for an unknown reason. - [#115](https://github.com/ned14/outcome/issues/115) - Outcome did not construct correctly from `failure_type`. - Inexplicably outcome's error + exception constructor had been removed. Nobody noticed during the Boost peer review, which is worrying seeing as that constructor is needed for one of the main advertised features to Boost! - [#107](https://github.com/ned14/outcome/issues/107) and [#116](https://github.com/ned14/outcome/issues/116) - `operator==` and `operator!=` now become disabled if the value, error and exception types do not implement the same operator. - Relatedly, both comparison operators simply didn't work right. Fixed. - [#109](https://github.com/ned14/outcome/issues/109) - `swap()` now has correct `noexcept` calculation and now correctly orders the swaps to be whichever is the throwing swap first. - Added reference dump of v2.1 ABI so we can check if ABI breakage detection works in the next set of changes, plus Travis job to check ABI and API compatibility per commit. - [#124](https://github.com/ned14/outcome/issues/124) - `OUTCOME_TRY` is now overloaded and selects `void` or `auto` edition according to input parameter count. - [#120](https://github.com/ned14/outcome/issues/120) - Fix generation of double underscored temporary variables in `OUTCOME_UNIQUE_NAME`, which is UB. - [#110](https://github.com/ned14/outcome/issues/110) - Separated `result` from its hard coded dependency on the `<system_error>` header. - Renamed `result` and `outcome` to `basic_result` and `basic_outcome`. - Renamed `result.hpp` into `basic_result.hpp`. - Moved `<system_error>` and `<exception>` dependent code into new `std_result.hpp` and `std_outcome.hpp` header files. - Added `boost_result.hpp` and `boost_outcome.hpp` which use Boost.System and Boost.Exception (these are `result.hpp` and `outcome.hpp` in the Boost edition). -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[beast] How do I select un-DEPRECATED interfaces?
by Brian Kuhl 04 Jun '18

04 Jun '18

Hi Experts, I’m working with an EAR release of VxWorks 7 with llvm v5.0 and VxWorks’ first C++14 STL ( Dinkum v700) and Boost v 1.67 ( Yes, the RTOS world moves slowly) I’ve gotten a clean compile of Beast with #define BOOST_BEAST_ALLOW_DEPRECATED #define BOOST_COROUTINES_NO_DEPRECATION_WARNING But I’m having trouble locating the logic that’s choosing these deprecated interfaces for me? Could someone point out the relevant logic? Many Thanks, Brian Kuhl Senior Manager – Information Development Wind River

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[Algorithm] contains(v, 1)
by Olaf van der Spek 03 Jun '18

03 Jun '18

Hi, vector<int> v; contains(v, 1); This doesn't work as contains expects two ranges (AFAIK). Is there some other function that's usable for this purpose? Should contains support a value for argument 2? Gr, -- Olaf

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[compressed_pair] [hof] [hana] What's the story with compressed_pair?
by Tom Westerhout 30 May '18

30 May '18

Hello! It looks like there are at least three different implementations of a "std::pair with EBO" in Boost: boost/utility/compressed_pair.hpp boost/hof/detail/compressed_pair.hpp boost/hana/pair.hpp Finally, there is also std::tuple which seems to also make use of EBO. I need similar functionality for a GSoC project I'm working on this year. So I'm wondering, is compressed pair considered a simple technicality that should be implemented from scratch every time I need it or shall I stick to one of the four mentioned implementations? I would much prefer to use Boost.Utility's one, but unfortunately it's neither constexpr-friendly nor noexcept-friendly... Is there some reason why it cannot be annotated with macros which expand to constexpr and noexcept when compiled with C++11 support? Or has no one just gotten around to do it? Thanks in advance, Tom

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[Hana] "basic_tuple.hpp" bug when building with VS2017
by Louis Dionne 30 May '18

30 May '18

> Hello, > > Just installed Boost and Visual Studio 2017 a few days ago. Visual Studio 2017 is known to be unable to compile Hana (and other libraries such as Range-v3). I will be working with the Microsoft folks to make it work as they explicitly reached out to me with that intent. Cheers, Louis

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