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

Scheduled Outage : Web sites / Trac
by Michael Caisse 17 Feb '17

17 Feb '17

We are planning the final move of services from IU this week. Expect service outages for all web sites including Trac on 17-February-2017 between 16:00 UTC - 00:00 UTC. The mail lists will continue to operate during this time; however, all other sub-domains for boost.org will be affected. Sync'ing bandwidth with IU has been low recently and has caused us to increase the outage window. We will notify these lists when services are available again. Thank you for your patience during the move. -- Michael Caisse Ciere Consulting ciere.com

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Boost.Python sandox or multiple interpreters
by David Bellot 17 Feb '17

17 Feb '17

Hi, I'm using Boost.Python to load and use plugins in Python. Each plugin can define a few functions which are are pre-determined, so that my C++ software knows what to call. However, the mistake I've made was to think that the Python interpreter could be initialized many times, so that each plugins was existing and running into a separate interpreter. It's of course not the case and therefore, each time I load a new plugin, its functions overwrite the functions of the same name from the previous plugin (the one which was loaded just before), and so on. Is there a possibility to either : - have as many independent Python interpreters at the same time ? - or encapsulate each plugin in an independent "environment" ? - or any other solution which would elegantly solve this problem ? :-D Thanks for your help, David

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[trac] how close trac for bug reports
by Oliver Kowalke 17 Feb '17

17 Feb '17

Hello, how can I close boost trac for a specific library? Users should report issues only at github. ty, Oliver

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[teeks] Missing winerror.h for MSVC-9
by Andrey Semashev 17 Feb '17

17 Feb '17

Hi, I see lots of tests failing on teeks99-09b-win2012R2-64on64, MSVC-9.0 because winerror.h is missing. Here's an example: http://www.boost.org/development/tests/develop/developer/output/teeks99-09b… I can see that the file is present in Windows SDK 6.0A, which is supposed to be used with this compiler. The tests are passing on my machine. Could this be a tester configuration issue? Also, all MSVC-15 tests are failing on teeks99-09o-win2012R2-64on64 with the error of 'cl' not being found.

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Functional programming in boost
by Abhishek Kumar 16 Feb '17

16 Feb '17

Hello I am a Computer Science senior from India. I have been doing functional programming for quite some time and have also used C++ for different projects. I recently came across BOOST libraries for supporting functional programming in C++. I want to contribute to one of the BOOST libraries maybe PHOENIX. Are there any open issues or plans in this direction, in which I might help? Thanks Abhishek Kumar

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[release] 1.64.0 deadline for new libraries approaching
by Rene Rivera 16 Feb '17

16 Feb '17

One week from today master will close for commits of new libraries. Thanks, -- The Boost Release Team -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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[safe_numerics] Review coming in March
by Andrzej Krzemienski 15 Feb '17

15 Feb '17

Hi Everyone, This is to inform you ahead of time that the formal review of Robert Ramey's Safe Numerics library will be held in about two weeks: March 2 - March 11. Boost Numerics is a set of drop-in replacements for the built-in integer types, which make the guarantee that the results of operations are either correct according to the rules of integer arithmetic or report a diagnosable error (rather than offering modulo arithmetic results, or resulting in undefined behavior, or returning incorrect results as in the case of signed vs. unsigned comparisons). The library can be found on GitHub: https://github.com/robertramey/safe_numerics/ Online docs: http://htmlpreview.github.io/?https://github.com/robertramey/safe_numerics/… Even before the formal review starts, you can provide your review on Boost Library Incubator: http://blincubator.com/reviews/?library_id=426 It will also be included in the final verdict. I will be making the official announcement on March 2. Andrzej Krzemienski, review manager.

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Is there any interest in non-owning pointer-like types?
by Joseph Thomson 14 Feb '17

14 Feb '17

For some time, I have been developing a pair of non-owning pointer-like types that I am currently calling `observer_ptr` and `observer`. I had planned to propose their addition to the C++ standard library, but I have been informed by the author of the original `observer_ptr` proposal <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4282.pdf> that the ISO C++ committee has rejected his proposal and made clear that it feels there is no place in the standard library for such types, believing that this role is filled to a satisfactory degree by regular pointers. I wholeheartedly disagree with this assessment, so I am bringing my proposal here instead. The `observer_ptr<T>` class template is a pointer-like type that does not do any resource management, and is intended to be used in place of `T*` wherever `T*` is used as a non-owning reference to an object of type `T`. `observer_ptr<T>` has three main advantages over `T*`: 1. `T&` is implicitly convertible to `observer_ptr<T>` which, unlike `T*`, makes it *type-safe*. `T*` can represent things that are not conceptually objects of type `T`: arrays, strings, iterators. No implicit conversion from `T*` means that these things cannot implicitly convert to `observer_ptr<T>`. Pointers aren't even required to point to valid objects (e.g. a past-the-end iterator). Conversely, in a well-formed program, `T&` is *always* a valid object of type `T`. 2. `observer_ptr<T>` documents its purpose. This is really a side-effect of it being type-safe (a type should have a single, specific purpose), but it's worth mentioning. Conversely, when you see `T*`, it may not be immediately obvious what it represents. 3. `observer_ptr<T>` has a minimal interface, which makes it harder to misuse than `T*`; for example, `observer_ptr<T>` has no pointer arithmetic operators, no array subscript operator, no conversion to `void*`. The `observer<T>` class template is a counterpart to `observer_ptr<T>` that has *no null state*; it cannot be default constructed, constructed from `nullptr_t` or constructed from `T*`, and it does not contextually convert to `bool`. The only way to create an `observer<T>` is from `T&`. This allows a "not null" precondition to be enforced at compile-time, rather than having to worry about pointers being null at run-time. Just to give you an idea of the current syntax, here is a simple tree node type (where the nodes do not own their children) implemented using `observer_ptr` and `observer`: class node { public: node() = default; node(node const&) = delete; node& operator=(node const&) = delete; node(node&&) = delete; node& operator=(node&&) = delete; void set_parent(observer_ptr<node> new_parent) { if (parent) parent->remove_child(*this); parent = new_parent; if (parent) parent->add_child(*this); } observer_ptr<node> get_parent() const { return parent; } size_t get_child_count() const { return children.size(); } observer<node> get_child(size_t index) const { return children[index]; } private: observer_ptr<node> parent; vector<observer<node>> children; void add_child(observer<node> child) { children.push_back(child); } void remove_child(observer<node> child) { children.erase(find(begin(children), end(children), child)); } }; And a contrived usage example: node a, b, c; b.set_parent(a); // conversion from `T&` c.set_parent(b); observer_ptr<node> x = c.get_parent(); if (x) // conversion to `bool` { observer<node> y = x->get_child(0); assert(y == c); // comparison with `T&` y->set_parent(a); b.set_parent(y); // conversion from `observer<T>` to `observer_ptr<T>` } A project with a working implementation <https://github.com/hpesoj/cpp-observer/blob/master/api/observer.hpp> and full test suite <https://github.com/hpesoj/cpp-observer/blob/master/tests/observer_tests.cpp> can be found here <https://github.com/hpesoj/cpp-observer>. Regards, Joseph

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What is http://downloads.sourceforge.net/boost/boost_1_63_0.tar.bz2 ?
by Jonathan Wakely 14 Feb '17

14 Feb '17

The link http://downloads.sourceforge.net/boost/boost_1_63_0.tar.bz2 redirects to http://downloads.sourceforge.net/project/boost/boost/snapshots/master/boost… which seems to be a snapshot from master, and VERY different to the boost_1_63_0 release (which makes it a VERY misleading URL). How often is that snapshot updated? Shouldn't it have a different name if it's not boost_1_63_0.tar.bz2 but some completely different set of sources (which currently don't even build)? The Fedora Linux packages have been using that URL, for several years by the look of things. So I have no idea what arbitrary collection of changes we've been shipping instead of a proper release.

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[test]redefinition of boost::unit_test::ut_detail::auto_test_unit_registrar
by Takatoshi Kondo 14 Feb '17

14 Feb '17

Hello, I'm using Boost.Test. When I define BOOST_AUTO_TEST_SUITE, I got a compile error 'redefinition of boost::unit_test::ut_detail::auto_test_unit_registrar' if the all following conditions are satisfied: 1. The test suite names are the same. 2. BOOST_AUTO_TEST_SUITE are defined in different files. 3. The files are included by one file. 4. BOOST_AUTO_TEST_SUITE are defined at the same line number. For example, main.cpp #define BOOST_TEST_MODULE test #include <boost/test/unit_test.hpp> #include "one.ipp" #include "two.ipp" one.ipp BOOST_AUTO_TEST_SUITE(a) BOOST_AUTO_TEST_CASE(tc1) { } BOOST_AUTO_TEST_SUITE_END() two.ipp BOOST_AUTO_TEST_SUITE(a) BOOST_AUTO_TEST_CASE(tc2) { } BOOST_AUTO_TEST_SUITE_END() Here is a live demo: http://melpon.org/wandbox/permlink/R459VQ6apnQfapyw If I insert a line the top of two.ipp, no errors are occurred. http://melpon.org/wandbox/permlink/jPRTstNDVb7agjXl According to the following document http://www.boost.org/doc/libs/1_63_0/libs/test/doc/html/boost_test/tests_or… "The same test suite can be restarted multiple times inside the same test file or in a different test files." The compile error is caused by the following line: https://github.com/boostorg/test/blob/develop/include/boost/test/unit_test_… If I replace BOOST_JOIN( BOOST_JOIN( test_name, _registrar ), __LINE__ ) \ with BOOST_JOIN( BOOST_JOIN( test_name, _registrar ), __COUNTER__ ) \ , then the error is disappeared. However, __COUNTER__ is not portable. I know that I can compile one.ipp and two.ipp separately, but I also want to have the option that include them from one file. Is there any good way to solve the error? Thanks, Takatoshi Kondo

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Lazy Spirit Generators?
by Christof Donat 14 Feb '17

14 Feb '17

Hi, In a hobby project, I am using Spirit Karma generators. As far as I have understood Spirit Karma, it is not designed to work lazily in the iterator based interface. It takes an output iterator and writes to it until it has finished. What I am thinking of is a kind of generating range. E.g.: for(auto& char: generator_range(double_ << " + " << double_ << "i", context, c.real(), c.imag())) { // do whatever with the single characters returned by the generator } Is there something like that, which I simply have not found? Christof

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Fit - Request for formal review
by Paul Fultz II 13 Feb '17

13 Feb '17

Hi, So I’ve made a lot of updates to the Fit library since last review. There are a few more changes I would like to make, but most of the work has been done. So, I would like to request for a formal review, and get it on the schedule soon. Vicente Botet was the review manager last time, I don’t know if he would be interested in being the review manager again. Is there perhaps someone else that would be interested in being review manager? https://github.com/pfultz2/Fit Thanks, Paul

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boost::aligned_storage is not a POD.
by Vicente J. Botet Escriba 11 Feb '17

11 Feb '17

Hi, boost::aligned_storage is not a POD. I suspect it is because of the declared constructors private: // noncopyable aligned_storage(const aligned_storage&); aligned_storage& operator=(const aligned_storage&); public: // structors aligned_storage() { } ~aligned_storage() { } Was this intentional? Why aligned_storage is not copyable? Best, Vicente

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[exception] error: looser throw specifier
by Niklas Angare 11 Feb '17

11 Feb '17

On QNX 6.6.0 with GCC 4.7.3 and Dinkumware library in -std=gnu++0x mode, I get the following error: ../libs/exception/test/throw_exception_test.cpp:21:1: error: looser throw specifier for 'virtual exception2::~exception2()' In file included from ../libs/exception/test/helper2.hpp:9:0, from ../libs/exception/test/throw_exception_test.cpp:6: ../boost/exception/exception.hpp:303:5: error: overriding 'virtual boost::exception::~exception() throw ()' libs/exception/test/throw_exception_test.cpp has these definitions: struct exception1: std::exception {}; struct exception2: std::exception, boost::exception {}; There is no error for exception1. Is the bug in the Boost library, the test, the compiler or the Dinkumware library? Other regression runners with GCC 4.7 don't get the error. My regression test runner is NA-QNX660-x86 so you can see all details in the result matrix. Regards, Niklas Angare

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Re: [boost] invalid access to stack memory?
by alexc 11 Feb '17

11 Feb '17

Original Message Sender:Bjorn Reese via Boostboost(a)lists.boost.org Recipient:boostboost@lists.boost.org Cc:Bjorn Reesebreese(a)mail1.stofanet.dk Date:Saturday, Feb 11, 2017 19:39 Subject:Re: [boost] invalid access to stack memory? On 02/11/2017 08:47 AM, alexc via Boost wrote: followed detail of the case, an object constructor store this pointer to a static variable. could it be a problem? From a quick look at the code, I do not think that it poses a problem. The idea, as I understand it, is to use RAII to push and pop a "stack frame" (call_stackT::context) onto a thread-local static "stack" (call_stackT::top_.) The context destructor will remove itself from the "stack". Oh, context class “recover” thecall_stackT::top_ indestructor, I miss this in the first place, thank you, Bjorn, it’s a very cool idea to me. _______________________________________________ Unsubscribe other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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Re: [boost] invalid access to stack memory?
by Bjorn Reese 11 Feb '17

11 Feb '17

On 02/11/2017 08:47 AM, alexc via Boost wrote: > followed detail of the case, an object constructor store this pointer to a static variable. could it be a problem? From a quick look at the code, I do not think that it poses a problem. The idea, as I understand it, is to use RAII to push and pop a "stack frame" (call_stack<T>::context) onto a thread-local static "stack" (call_stack<T>::top_.) The context destructor will remove itself from the "stack".

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invalid access to stack memory?
by alexc 11 Feb '17

11 Feb '17

Hi all, followed detail of the case, an object constructor store this pointer to a static variable. could it be a problem? detail/call_stack.hpp explicit context(Key* k) : key_(k), next_(call_stackKey, Value::top_) { value_ = reinterpret_castunsigned char*(this); call_stackKey, Value::top_ = this; // == store this to a static variable } detail/impl/strand_service.ipp void strand_service::do_complete(io_service_impl* owner, operation* base, const boost::system::error_code ec, std::size_t /*bytes_transferred*/) { if (owner) { strand_impl* impl = static_caststrand_impl*(base); // Indicate that this strand is executing on the current thread. call_stackstrand_impl::context ctx(impl); // == local variable ctx, its this pointer will be stroed in a static variable. Regards, Alex

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Review Request : Boost.SIMD
by Joel FALCOU 10 Feb '17

10 Feb '17

Can Boost.SIMD please be added to the review queue? Michael Caisse has volunteered to act as the review manager. Boost.SIMD is an efficient modern C++ wrapper for SIMD instructiosn sets and computations that aims at providing a standard way to write code taking advantages of SIMD enabled hardwares. Boost.SIMD repository https://github.com/NumScale/boost.simd Documentation https://developer.numscale.com/boost.simd/documentation/develop/ Thanks in advance Joel Falcou - CTO @ NumScale

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Testing DMARC spam binning
by Niall Douglas 10 Feb '17

10 Feb '17

Dear Boost, You all probably noticed that boost-dev now sends you emails from "Your Name via Boost <boost(a)lists.boost.org>" with your original email listed as CC. This should finally mean that DMARC protected email addresses are no longer flagged as Spam by many email services, including this email from me, as boost-dev is no longer sending email with a protected From: address. The list should be made aware that fixing this has taken nine months or so for good reason. A whole ton of work went into making this happen, not least relocating Boost's mailing list services from wowbagger where it had been for almost forever to new hosting partially donated to us for free. What wasn't obvious here was that there were problems of ownership transfer, arranging service donation and the change over and getting many, many long seized up cogs to turn, ones indeed I have failed to turn in many years of trying myself. The fact it all happened without service interruption is an amazing achievement. I'd like to ask the list to formally thank Michael Caisse and his team of many diligent workers who did all of this just to get mail posted here to not get flagged as Spam (there were other motivating factors too of course, but the Spam issue got the ball rolling). It was an awful lot of work for not a very obvious gain here on boost-dev. So thank you. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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Re: [boost] Requirements: min and max macros
by Bjorn Reese 07 Feb '17

07 Feb '17

On 02/05/2017 06:15 PM, Vinnie Falco wrote: > From > http://www.boost.org/development/requirements.html#Naming > > "Make sure your code compiles in the presence of the min() and max() > macros. Some platform headers define min() and max()macros which cause > some common C++ constructs to fail to compile. Some simple tricks can > protect your code from inappropriate macro substitution:..." Is this guideline still relevant?

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[gsoc17] Attn: We need 2017 mentors and project ideas for Boost!
by Niall Douglas 07 Feb '17

07 Feb '17

Dear Boost community, We are now a few weeks from the beginning of Google Summer of Code 2017! Last year we had the big surprise of being rejected by Google as an org, the second time ever, on the basis that Google felt we needed a year off. Thanks to the quick actions of the Boost Steering Committee and IMC Financial Markets we managed to put together a "Boost Summer of Code" so the students with projects in progress would not be left stranded. Despite a fair few teething problems, I think that worked out okay. As part of filling in our application for 2017, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2017 in order to be approved as an organisation this year. Therefore a lengthy page of awesome project ideas at https://svn.boost.org/trac/boost/wiki/SoC2017 before *February 9th* would be an enormous help to getting us approved again this year and bringing to Boost another US$35,000 of Google funding. If you think yourself able to mentor a student doing some work on Boost this summer, *please* consider adding a description of the proposed work item and your name to the list. The year before last we had more slots awarded to us by Google than we had good combinations of student and mentor, so we had to return slots which I believe has not happened here at Boost GSoC in at least a decade. That means that your project ideas have a better chance than ever of receiving funding if you can find a good student, and that is best done by getting project ideas floated *early*. If you want to know more about mentoring a Google Summer of Code funded student work before you nominate yourself, please feel free to ask on the main Boost developers mailing list boost(a)lists.boost.org or via gsoc-admin(a)boost.org. Thank you in advance for your time.

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[interprocess] Fix doc build ASAP
by Rene Rivera 07 Feb '17

07 Feb '17

This commit < https://github.com/boostorg/interprocess/commit/936afb13f0c106728bcf36c1ce1…> seems to have broken the release archive documentation build: Generating Output File: /home/ubuntu/build/boost/bin.v2/libs/interprocess/doc/docbook/gcc-4.9.2/debug/interprocess.xml /home/ubuntu/boost/libs/interprocess/doc/interprocess.qbk:7421: error: Mismatched [endsect] near column 9. Error: Error count: 1. Please fix ASAP. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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[GIL] Bringing old bug fixes on development branch into regular boost releases
by Marcel Metz 06 Feb '17

06 Feb '17

Hello boost devs, I'm a user of the Boost.GIL library and maintained a fork inside inside another project because GIL lacked some features at that time this project needs. This GIL fork happened with boost release 1.37. After reviewing the changes recently it turned out that those can be implemented without maintaining a dedicated GIL fork. However when building the project with the upstream GIL library some compiler specific build bugs popped up. It seems like the forked GIL version already had fixes for those whereas the upstream Boost.GIL doesn't. Further investigation showed that some of those were fixed years ago in the GIL development branch, but never made it back into the master branch (and as far as I understand master is used for release tags). All of those were reported: #3908 - using boost::gil fails when upgrading to libpng-1.4.0 #7270 - C++11 narrowing problem in gil #8896 - image_view compile error under clang 3.1 #9517 - boost gil compile error because of type narrowing (dup of #7270) Is it possible for the maintainer to cherry-pick the corresponding commits from development onto master and put them into the next boost release or are there other steps involved that prevent the bug fix inclusion? Regards Marcel

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[Fit] Update: Request for feedback
by Paul Fultz II 06 Feb '17

06 Feb '17

Hi, I have made a lot of updates to the Fit library based on the changes suggested during the review earlier this year. I have also improved the documentation. I have expanded on the introductory materials and have add a lot more cross-referencing. The documentation can be found here: http://fit.readthedocs.io <http://fit.readthedocs.io/> Let me know of any feedback about the library either here on the mailing list or on Github issues. Thanks, Paul

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Requirements: min and max macros
by Vinnie Falco 05 Feb '17

05 Feb '17

From http://www.boost.org/development/requirements.html#Naming "Make sure your code compiles in the presence of the min() and max() macros. Some platform headers define min() and max()macros which cause some common C++ constructs to fail to compile. Some simple tricks can protect your code from inappropriate macro substitution:..." There is one case not addressed. What to do with this: std::min<std::size_t>(a, b); ?

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