December 2017 - Boost - lists.preview.boost.org

[foreach][polygon][xpressive][bimap][ptr_container][gil][assign][typeof][msm] PRs for removing executable attribute for files
by Edward Diener 08 Mar '18

08 Mar '18

The following libraries still have PRs, which I have previously submitted, for removing the executable attribute for one or more files: foreach polygon xpressive bimap ptr_container gil assign typeof msm None of these PRs affect anything other than the file attribute, so no testing is needed AFAICS since no code changes. If the maintainers of the above libraries, or someone else with write access to these libraries, can merge the appropriate PR to 'develop', and then merge 'develop' to 'master', we can get rid of having any files with their executable attribute set in the next release.

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[yap] Re-announcing Yap
by Zach Laine 23 Feb '18

23 Feb '18

I posted 2-3 months ago about Yap, an expression template library I've written that I intend to propose for Boost. This is just a reminder that the library exists, and where to find it. I'm giving a talk about it at C++Now 2017, and some time after that I intend to submit it to the queue. Louis Dionne has offered to serve as review manager when the time comes. You can find the main repo on GitHub: https://github.com/tzlaine/yap And online docs are here: https://tzlaine.github.io/yap Zach

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[Root Pointer] Deterministic C++ memory manager (update)
by Phil Bouchard 26 Jan '18

26 Jan '18

Greetings, I wanted to give an update to the community regarding the memory manager I wrote called: Root Pointer. I now have a working template to solve all memory leaks in C++ and C but both requires some meta data generator. The code can be found here; it is working but not polished: https://github.com/philippeb8/root_ptr In this code we can find: - node_ptr: main class of the smart pointer / memory manager. - root_ptr: generic derived class that includes an "iterator" and a pointer to the name of the instance (for debugging purposes). Also I commented some code that logs the exact location of the memory leak. Furthermore I would like to bring some observations that I found in the C and the C++ language: - Pointers and iterators are not the same; i.e. pointers should point to allocated blocks only and shouldn't have arithmetic operators while iterators shouldn't be used to deallocate anything. - C pointers can only point to dynamic arrays (size known at run-time). - C++ pointers can point to both inherited objects and static arrays (size known at compile-time). This creates a problem (see attached: array_inherited_pointer.cpp). - std::array<T> should have constructors with T objects that have no default constructor. Lastly, before I submit anything, I will have to propose a way to apply a template function to all non-static member variables of a class. This will require implicit meta data generation. This idea is not new as other libraries such as Qt is based on meta data and they certainly could make us of this. For the moment I have a parser that does the job correctly by specializing a boost::proxy() template function but eventually this will have to be integrated into the standards. Hopefully this is an important milestone! Regards, Phil Bouchard www.fornux.com

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[config] Supporting newer compilers: what does it take?
by Olaf van der Spek 22 Jan '18

22 Jan '18

Hi, What does it take to support new compilers, especially MSVC? 15.6 Preview 1 has been released now. Is some documentation or policy regarding test runners etc available? https://blogs.msdn.microsoft.com/vcblog/2017/12/19/c17-progress-in-vs-2017-… Gr, -- Olaf

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Informal CMake meeting at CPPCon
by Robert Ramey 12 Jan '18

12 Jan '18

Thursday 28 Sept 8 AM at CPPCon a small group of us met to talk a little regarding the situation regarding support of CMake by Boost. I promoted this meeting as I've been concerned that the only discernible results of the recent Boost Steering Committee announcement on the subject was a certain level of antagonism among boost members regarding the subject. Participants ============ Robert Ramey (me) Rene Rivera Vinnie Falco Louis Dionne David Sankel Matt Calabrese This was a small but I think a representative group. After some preliminary back and forth, I think we agreed: a) Nothing was going change regarding the current build system until there was a real alternative in place. b) That we should support serious proposals to implement CMake support within boost. c) And that any such proposals should go through the Boost formal review process. Traditionally, the boost formal review process has never applied to boost tools so this would be a departure from traditional practice. d) Questions regarding the scope/implemention of such support for CMake can be handled within the formal review process. e) Other questions regarding support CMake and Boost, transition to new system, related requirements on boost libraries, etc. can be better addressed once we have some sort of consensus on the form that CMake support will take. I had contacted Paul Fultz who is the only one I know of that has proposed something specific to submit to formal review. He told me he couldn't do it at the time, but shortly there after posted such a request on the list. So I guess for now we're on our way. My motivation for posting this is to keep the boost community up to date on what's happening so that no one gets overly surprised when things start to happen. I'm not really soliciting feedback - though it wouldn't surprise me if I get some. Robert Ramey

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Re: [boost] seeking endorsement for histogram library
by Bjorn Reese 09 Jan '18

09 Jan '18

I endorse boost.histogram.

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[hash] Extract module from functional + std::hash_combine
by Daniel James 06 Jan '18

06 Jan '18

Hi, I'm planning to extract hash from functional into its own module, as that will apparently break the circular dependencies that functional is part of. Any objections? Also, any opinions on what the module should be called? 'hash' might suggest a more general purpose hash function, so maybe it should be called something more specific. Daniel

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Interest for a Fixed Point Arithmetics library
by Julien Vernay 03 Jan '18

03 Jan '18

Hello everybody. I am working on a project that needs and can use fixed point numbers, so I started searching for a library implementing fixed point numbers, but I didn't find anything. So I was wondering if people would need fixed point arithmetics, and here I am. The aim of this FixedPointNumber is to fix the point at compile-time using template, and having another template argument for the underlying type. So we have : template<typename T, size_t N> class FixedPointNumber { T value; public: //interface }; The N last bits of value is the decimal part : so to convert a FixedPointNumber to an int, we need only to use a bitshift operator (and same for construction from int). sizeof(FixedPointNumber<T,N>) == sizeof(T) , so there is no overhead in this implementation. Arithmetic and relational operators will be implemented. Multiplication needs one int multiplication and one bit shift. Division needs one int division and one bit shift. There is only one value for zero. Sign can be extracted with Most Significant Bit. I have already a basic implementation but if it interests more people I will do a proper implementation. Thank you for reading !

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[multiprecision] Help needed with strange constexpr slowdown
by John Maddock 03 Jan '18

03 Jan '18

Folks I have a very strange issue that I need help with understanding, it comes from https://github.com/boostorg/multiprecision/issues/32 but in summary: Given: #include <iostream> #include <boost/multiprecision/cpp_int.hpp> using namespace std; using namespace boost::multiprecision; int main() { __int128_t i =0; __int128_t j =0; int256_t sum =0; for (; i <1e9; i +=19, j +=13) { int256_t diff = j; sum += i * diff; } std::cout <<"Result: " << sum << std::endl; return 0; } There is a 20-30% slowdown when compiled in C++11 or later compared to C++03 with gcc 5.x or 6.x. I've tracked this down to the constexpr default constructor for int256_t (which is called inside operator* to create a temporary for the result), if I make the default constructor non-constexpr by removing BOOST_CONSTEXPR from any of: number.hpp:44 (number()) cpp_int.hpp:1077 (cpp_int_backend()) cpp_int.hpp:501 (cpp_int_base()) cpp_int.hpp: 435 (cpp_int_base::data_type()) Then the slowdown disappears. All the line numbers refer to current develop BTW. gcc-7 is better, but I notice it still generates different code if the constructor is constexpr - that greatly surprises me to be frank - is there something I'm missing about constexpr-ness that could cause this? Confused yours, John. --- This email has been checked for viruses by AVG. http://www.avg.com

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Re: [boost] Boost.HTTPKit, a new library from the makers of Beast!
by Vinnie Falco 01 Jan '18

01 Jan '18

On Sun, Oct 8, 2017 at 5:38 PM, Vinícius dos Santos Oliveira <vini.ipsmaker(a)gmail.com> wrote: > Now, moving on... given that you have __not__ answered how your parser's > design[1] compares to the parser I've developed I'll try to provide more clarity. `beast::basic_parser` is designed with standardization in mind, as I intent to eventually propose Beast for the standard library. Therefore, I have made the interface as simple as possible, exposing only the minimum required necessary to achieve these goals which the majority of users want: * Read the header first, if desired * Feed Asio style buffer sequences into the parser * Set independent limits on the number of header and body octets * Optional fine-grained receipt of chunked body data and metadata The design of basic_parser (the use of CRTP in particular) is meant to support the case where a user implements their own Fields container, or if they want a bit more custom handling of the fields (for example, to avoid storing them). Like all design choices, tradeoffs are made. The details of parsing are exposed only to the derived class. Complexities are hidden from the public-facing interface of `basic_parser`. Implementing a stream algorithm that operates on the parser is a straightforward process: template< class SyncReadStream, class DynamicBuffer, bool isRequest, class Derived> std::size_t read(SyncReadStream& stream, DynamicBuffer& buffer, basic_parser<isRequest, Derived>& parser, error_code& ec) { parser.eager(true); if(parser.is_done()) { ec.assign(0, ec.category()); return 0; } std::size_t bytes_transferred = 0; do { bytes_transferred += read_some( stream, buffer, parser, ec); if(ec) return bytes_transferred; } while(! parser.is_done()); return bytes_transferred; } > [1] at most it hides behind a “multiple people/stakeholders agree with me” > __shield__ There's no hiding going on here. One can only measure the relative success of designs based on the feedback from users. They opened issues, and I addressed their use-cases, sometimes with a considerable amount of iteration and back-and-forth as you have seen in the GitHub issues quoted in the previous message. Now, I don't know if the sampling of users that have participated in Beast's design are representative of the entire C++ community. However, I do know one thing - if GitHub stars are any measure of the sample size of the participants, then Beast is off to a good start. Here's a graph showing the number stars over time received by boostorg/beast, tufao, and Boost.Http (the last 2 libraries having you as the author I believe): <http://www.timqian.com/star-history/#boostorg/beast&BoostGSoC14/boost.http&…> (Note that the HTTP+WebSocket version of Beast was released in May 2016). We need to be careful interpreting results like this of course so perhaps we should look at different metrics. Here are the links to the number of closed issues for Beast, tufao, and Boost.Http: 502 Closed issues in Beast: <https://github.com/boostorg/beast/issues?q=is%3Aissue+is%3Aclosed> 38 Closed issues in tufao <https://github.com/vinipsmaker/tufao/issues?q=is%3Aissue+is%3Aclosed> 13 Closed issues in Boost.HTTP, from 6 unique users not including the author <https://github.com/BoostGSoC14/boost.http/issues?q=is%3Aissue+is%3Aclosed> Again we have to be careful interpreting results like this. But it sure looks like there is a lot of user participation in Beast. If approval from a large number of stakeholders is not a compelling design motivator then what is? > This tutorial is full of “design implications” blocks where I take the time > to dissect what it means to go with each choice. Thus far, no one has asked for more fine grained access to incoming HTTP tokens in the manner of `code::method` and `code::request_target`. If this becomes something that users consistently ask for, it can be done by changing the requirements for the derived class for `basic_parser`. This way, details about HTTP parsing which most people don't care about will not leak into the beast::http:: namespace. Such a change would not affect existing stream algorithms on parsers. Thanks

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Re: [boost] What hash functions should be included in a hypothetical Boost hash-v2 library?
by Bjorn Reese 31 Dec '17

31 Dec '17

On 12/31/17 01:28, Peter Dimov via Boost wrote: > What (non-cryptographic) hash functions should a hypothetical future > Boost hash library contain? Have clear winners emerged by now? Which > ones do people prefer? I vote for FNV hashes: https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function

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What hash functions should be included in a hypothetical Boost hash-v2 library?
by Peter Dimov 31 Dec '17

31 Dec '17

What (non-cryptographic) hash functions should a hypothetical future Boost hash library contain? Have clear winners emerged by now? Which ones do people prefer? SipHash is basically a given, but it's not optimized for speed.

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Removing hash from Boost.Functional broke modules
by James E. King, III 28 Dec '17

28 Dec '17

See: https://github.com/boostorg/type_index/issues/18 There is no forwarding header to keep things compatible. - Jim

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Maintenance of Boost.DateTime
by James E. King, III 28 Dec '17

28 Dec '17

The backlog for Boost.DateTime in trac has over 130 issues; the project is holding on to very old backwards compatibility code (pre-boost-1.33.0 i/o facets), and the CI builds do not currently have appveyor, codecov.io, or coverity scan integration. It needs a proper maintainer in order to resolve these issues, so I would like to ask for that privilege. Thanks, Jim

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Appveyor and Travis CI notifications of Boost library tests
by Edward Diener 26 Dec '17

26 Dec '17

Is there a way to tell Appveyor or Travis CI to send notifications of its Build runs of Boost libraries to someone other than myself ?

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Candidate for 1.66.1, if there is one
by James E. King, III 25 Dec '17

25 Dec '17

In Boost 1.66.0, there was a fix to date_time for the year 2038 problem: https://github.com/boostorg/date_time/pull/35 The serialization code in date_time had no static assertions enforcing the size of data values, and adding proper versioning support was missed in the release by myself and not picked up in the code reviews. As a result, serializing in anything written by earlier boost versions fails for date_time related structures, which might be considered serious enough to justify a 1.66.1 release. (We could also get the latest msvc compatibility in there I suppose...) I'm adding proper versioning right now, however Boost 1.66.0 will remain a problem since it serializes in/out as Version 0 with 64-bit values; and 1.65.1 serializes in/out Version 0 with 32-bit values so I'm not certain there will be a way to detect this issue. The issue is recorded in github here: https://github.com/boostorg/date_time/issues/56 Any additional thoughts are appreciated. I'm looking at adding a test to write out a version 0 and then read it in when the current version is 1, but I don't want to add test-only support code to the headers that get shipped, so if anyone can point me at a current example unit test that writes out a "n-1" version and then reads in a "n" version with boost::serialization I would appreciate it. Thanks, Jim

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Getting Started
by ishan garg 25 Dec '17

25 Dec '17

Hello everyone, I am new to OpenSource Development. I know basics of C++ and acquainted with it's STL. I have basic knowledge of DSA as well as few git commands (clone, push, commit, etc). I wanted to know how can I start contributing to BOOST library? Thanks in Advance -- Regards, Ishan Garg

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library maintainer list
by Robert Ramey 24 Dec '17

24 Dec '17

I'm curious about how I might go about discovering and contacting the person(s) who might be maintaining a particular library. As an example, I have a couple of questions about possible enhancements to the boost interval library (what about making this constexpr?). Ideally, I'd like to see a summary page for each library which steers me to the appropriate links like issues, comments/issues page, maintainence status etc. such as the boost library incubator has. Actually, I considered just adding these pages to the boost library incubator website, but I didn't have the motivation and it might stir a pot I personally don't want to stir right now. Robert Ramey

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regarding mailing list traffic
by Mudit Sharma 22 Dec '17

22 Dec '17

Dear All, I have recently not been receiving the daily Boost mailing list digest, is there some maintenance work going on ? Thanks! M

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[date_time] Trac 13194 - %e posix time_input_facet specifier behavior
by James E. King, III 21 Dec '17

21 Dec '17

https://svn.boost.org/trac10/ticket/13194 Just looking at this one, and looking at the documentation, it states that %e is the same as %d however when the value is less than 10, a leading space is to be used instead of a leading zero. The example in the description has a flaw, I believe, and I commented on that. Do folks agree with my comment? Should parsing fail if it says "December 5" (with one space) and the format string is "%B %e"? Valid input would be "December 5" (with two spaces). I also found that the code blindly ignores delimiter specifiers, so I opened a github issue for it: https://github.com/boostorg/date_time/issues/53. Comments appreciated there as well. Thanks, Jim

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[endian] undefined behaviour in boost.endian
by Arvid Norberg 21 Dec '17

21 Dec '17

Hi, I've submitted an issue to the github project for boost.endian. I'm starting to wonder if this is in fact not the preferred channel for reporting issues. There are at least two separate issues causing undefined behaviour to be invoked in boost.endian. The first one is fundamentally based on the assumption that if the target architecture is x86, the C++ alignment requirements don't apply. I've posted more details here: https://github.com/boostorg/endian/issues/21 with a proposed patch here: https://github.com/boostorg/endian/pull/22 The second issue involves shifting negative integers, both invoking implementation defined and undefined behaviour. I don't have a patch to fix the issue, just to extend the tests to exercise the problem, which is then detectible with the undefined behaviour sanitizer. Patch is here: https://github.com/boostorg/endian/pull/24 I would really appreciate it if someone could review these and/or suggest a better venue than github to propose patches. thanks! -- Arvid Norberg

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[build] Currently broken with Xcode 8?
by John Maddock 20 Dec '17

20 Dec '17

Current develop appears not to build with XCode 8.0 causing Travis tests to fail, for example: https://travis-ci.org/boostorg/config/jobs/318188889 Thanks, John. --- This email has been checked for viruses by AVG. http://www.avg.com

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[release] Boost 1.66.0
by Daniel James 19 Dec '17

19 Dec '17

Release 1.66.0 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 N new libraries and numerous enhancements and bug fixes for existing libraries. For details, including download links, see <http://www.boost.org/users/news/version_1.66.0> You can also download directly from: <https://dl.bintray.com/boostorg/release/1.66.0/> To install this release on your system, see <http://www.boost.org/doc/libs/release/more/getting_started/index.html> Thanks to everyone who participated in this release. Thanks, -- The Boost Release Team Vladimir Prus, Marshall Clow, Eric Niebler, Daniel James, Beman Dawes

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[release] 1.67.0 open for merging
by Daniel James 19 Dec '17

19 Dec '17

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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[release] 1.66.0 post-beta merges
by Daniel James 19 Dec '17

19 Dec '17

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/Release-Beta-Merge-Policy>

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