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

[outcome] Requesting second pre-review of Boost.Outcome tutorial
by Niall Douglas 27 Jan '17

27 Jan '17

Dear Boost, Last November you gave me some valuable feedback on rewriting the tutorial for Boost.Outcome, a C++ 14 library providing a factory and family of policy driven lightweight monadic value-or-error transports. I recently came out of employment contract and so have had the time to rewrite Outcome's Tutorial (anyone interested in employing a remote working C++ consultant please do get in contact). I'd appreciate feedback on https://ned14.github.io/boost.outcome/: 1. Is this rewritten tutorial too simple, too detailed or about right? 2. Do you feel you could use Outcome in your own code without difficulty after reading it? If not, what information is missing? 3. Are you persuaded of the merits of using Outcome after reading it? If not, what else do I need to say? The first FOUR sections at https://ned14.github.io/boost.outcome/ have been rewritten by me to hopefully reflect the feedback you gave me last November, so these have been refactored so far: * Description, Prerequisites and Support * Installing, building and testing Outcome * Quick start for the expert * Tutorial The package repo install methods haven't been implemented yet, these are marked in the docs as todo. These sections have yet to be refactored: * Frequently Asked Questions * Advanced usage: Outcome as a Monad * Outcome and the upcoming std::expected<T, E> Many thanks in advance for any feedback received. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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Why is this message in Spam?
by Olaf van der Spek 26 Jan '17

26 Jan '17

Hi, > Why is this message in Spam? It has a from address in microsoft.com but has failed microsoft.com's required tests for authentication. Learn more I think this list isn't configured properly.. and this causes some messages to end up in Spam consistently.. Who's responsible for the mailing list infrastructure? Gr, -- Olaf

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[sort] pdqsort
by Steven Ross 26 Jan '17

26 Jan '17

I've been reviewing a proposed addition to Boost.Sort called pdqsort. When using a general-case partitioning algorithm, it performs comparably to std::sort in my testing (Windows and Linux). When used as a replacement for the std::sort fallback in spreadsort, using a branch-reducing optimization it is ~20% faster on ints and floats, and ~40% slower on strings. The concerning part is that any comparison operator that involves a branch may have a comparable slowdown to the string case. pdqsort is also significantly faster than std::sort on mostly-sorted data and some other (relatively common) special cases. This makes little difference when used as a fallback by spreadsort, but does make a difference when used on its own. I see these possible things to do with pdqsort: 1) Reject it completely as too similar to std::sort, which is already highly optimized. 2) Add it as another optional library in the Boost.Sort library. 3) Add it to Boost.Sort, and only use it as a fallback for ints and floats. 4) Add it to Boost.Sort, use it as a fallback for all of spreadsort, and have pdqsort itself only use its branch-reduction optimization on ints and floats. 5) #4, except eliminate the branch-reduction optimization completely from pdqsort for simplicity. Does anyone have a strong preference, advice, or comments on how they use Boost.Sort? Should I run a mini-review for pdqsort?

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Re: [boost] bad include guards
by Larry Evans 26 Jan '17

26 Jan '17

On 08/21/2007 03:11 PM, Steven Watanabe wrote: > AMDG > > The following pairs of files have identical include guards > > ./boost/concept_check/general.hpp ./boost/concept/detail/msvc.hpp > ./boost/concept_check/msvc.hpp ./boost/concept/detail/msvc.hpp > ./boost/filesystem/cerrno.hpp ./boost/cerrno.hpp > ./boost/interprocess/containers/tree.hpp > ./boost/interprocess/containers/detail/tree.hpp . . . Steven, do you have a program to detect files with identical include guards. I could you one at the moment :) -regards, Larry

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Boost XML Serialization Stability across library versions
by Adlai Shawareb 26 Jan '17

26 Jan '17

Hi, We want to generate an Serialized XML archive now, and be able to deserialize it and get the same data it in the future. Is Boost XML Serialization guaranteed to be compatible across versions of the library? The XML serialized archive would be stored in a memory chip and, in the future, read back and deserialized. I don't believe that would impact the answer, but want to offer that. Adlai

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Moving away from SourceForge
by Louis Dionne 26 Jan '17

26 Jan '17

Hi, I know this has been discussed in the past, but I would like to revive the discussion about moving away from SourceForge as Boosts' release hosting provider. SourceForge has at least the following issues: - There is no way of controlling the format when downloading an archive of the latest release. This can break people that rely on this in their CI scripts. For example, Metabench's[1] CI was broken for a while when the archive changed from .bz2 to .zip. - SourceForge has been in the middle of some controversies[2]. - Their reliability has not been so great. In the past year, I've had quite a few of my Travis jobs fail due to SourceForge being unresponsive. There are most likely other concerns, but these are the ones that really bite me as a user right now. Am I the only one? If there's some push to do the move, the two main candidates I see would be - GitHub's native hosting - Bintray Thoughts? Louis [1]: https://github.com/ldionne/metabench [2]: https://en.wikipedia.org/wiki/SourceForge#Controversies -- View this message in context: http://boost.2283326.n4.nabble.com/Moving-away-from-SourceForge-tp4691184.h… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Boost.Endian - endian_buffer requirements
by Vicente J. Botet Escriba 26 Jan '17

26 Jan '17

Hi, I wanted to put an Int wrapper inside a endian_buffer and I have some compiler errors depending on whether it is aligned ort not. http://melpon.org/wandbox/permlink/k52wH2A7yagL2vMP I was expecting that the endian_buffer would make abstraction of the wrapped type and consider it just as a sequence of bytes, but it seems that it instead works only for some builtin integral. Am I missing something? Was this restriction intended? Could this restriction be removed and if yes, how? Best, Vicente

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[program_options] implicit value and non-adjacent tokens
by Vladimir Prus 25 Jan '17

25 Jan '17

Hi, some time ago, program_options was modified so that options with implicit value would only take value from the same token. Previously, one could have: ./program -a foo -b # uses 'foo' as value for 'a' ./program -a -b # uses some default value for 'a' ./program -b # has no value for 'a' Now, the first syntax interprets 'foo' as positional option, and one has two write ./program -a=foo Ever since, I hear concerns from users about this behavior. Maybe not very loud, but quite consistent. Maybe, the new behavior is not very good, indeed, because it now mixes syntax matter (whether value is in the same token) with semantic matter (whether an option has implied value). I am considering reverting this change for next version of Boost. Does anybody have opinions either way? Thanks, Volodya

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C++Now / BoostCon 2017 -- Call For Submissions
by Michael Caisse 23 Jan '17

23 Jan '17

This is a quick reminder that the C++Now 2017 Call For Submissions is *open*. All submissions must be made by February 3rd. For more information, see http://cppnow.org/

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boost build with emscripten
by Emil Dotchevski 23 Jan '17

23 Jan '17

I see that there is now emscripten support in boost build but it doesn't seem to work for me. After installing emscripten on Windows, adding using emscripten ; in my site-config.jam, then running b2 from the emscripten command prompt, I get the output below. Any help greatly appreciated! Emil boost-build/src/build\property.jam:743: in class(a)property-map.find from module object(property-map)@26 error: Ambiguous key boost-build/src/build\type.jam:333: in generated-target-ps from module type boost-build/src/build\type.jam:270: in type.generated-target-suffix from module type boost-build/src/build\virtual-target.jam:509: in virtual-target.add-prefix-and-suffix from module virtual-target boost-build/src/build\virtual-target.jam:468: in _adjust-name from module object(file-target)@3764 boost-build/src/build\virtual-target.jam:253: in abstract-file-target.__init__ from module object(file-target)@3764 boost-build/src/build\virtual-target.jam:561: in class(a)file-target.__init__ from module object(file-target)@3764 boost-build/src/kernel\class.jam:90: in class.new from module class boost-build/src/build\generators.jam:558: in generated-targets from module object(C-compiling-generator)@138 boost-build/src/build\generators.jam:453: in construct-result from module object(C-compiling-generator)@138 boost-build/src/build\generators.jam:412: in run-really from module object(C-compiling-generator)@138 boost-build/src/build\generators.jam:386: in class(a)generator.run from module object(C-compiling-generator)@138 boost-build/src/build\generators.jam:994: in try-one-generator-really from module generators boost-build/src/build\generators.jam:1056: in try-one-generator from module generators boost-build/src/build\generators.jam:1294: in construct-really from module generators boost-build/src/build\generators.jam:1378: in generators.construct from module generators boost-build/src/build\targets.jam:1553: in construct from module object(typed-target)@3554 boost-build/src/build\targets.jam:1353: in class(a)basic-target.generate from module object(typed-target)@3554 boost-build/src/build\targets.jam:774: in generate-really from module object(main-target)@3735 boost-build/src/build\targets.jam:746: in class(a)main-target.generate from module object(main-target)@3735 boost-build/src/build\targets.jam:895: in targets.generate-from-reference from module targets boost-build/src/build\targets.jam:1266: in generate-dependencies from module object(typed-target)@2173 boost-build/src/build\targets.jam:1323: in class(a)basic-target.generate from module object(typed-target)@2173 boost-build/src/build\targets.jam:774: in generate-really from module object(main-target)@2988 boost-build/src/build\targets.jam:746: in class(a)main-target.generate from module object(main-target)@2988 boost-build/src\build-system.jam:714: in load from module build-system NT\..\..\munch\boost-build\src\kernel\modules.jam:295: in import from module modules NT\..\..\munch\boost-build\src\kernel\bootstrap.jam:139: in boost-build from module NT\..\..\munch\boost-build.jam:6: in module scope from module

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Re: [boost] [interprocess] Getting boot-up time is unreliable on Windows
by Ion Gaztañaga 23 Jan '17

23 Jan '17

On 22/12/2016 10:01, Thomas Dahms wrote: > Dear developers, dear Ion, > > We are experiencing issues on Windows where boost::interprocess relies > on a certain event in the system event log to get the system's boot-up > time. This has proven to be unreliable, because that event is not always > present in the log. In that case, initialization of boost::interprocess > fails. > Several bug reports exist for that issue, e.g. [1, 2]. > > Report [1] contains a proposed fix to use GetTickCount64() and there is > an open PR with an alternative fix to fall back to WMI mechanisms [3]. I > understand that the fix [1] would need some polishing, because > GetTickCount64() is not available in pre-Vista. > > Nevertheless, both proposed fixes have been uncommented and unconsidered > for a while now. Is there any chance that the maintainers could look > into this? Thanks for the ping. I don't think GetTickCount64 is very reliable, as other methods also have problems with time correction, hibernation, fast bootup, etc. In [1] one the last bootup log is lost new processes won't be able to communicate with others. The same happens with [3] In http://www.boost.org/doc/libs/1_63_0/doc/html/interprocess/acknowledgements… there are some instructions to give up on kernel persistence and define the directory at compile time or run-time. This is the best workaround so far. I've trying to find a solution with no luck. I tried: HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters\BootId in modern Windows systems but hybrid shutdown (default since Windows 8) does not seem to update it as kernel is suspended. Searching for a unique bootup id in windows that does not suffer when hibernating or correcting the RTC is really complicated. Any suggestion welcomed. Best, Ion

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[serialization][test] failures in serialization causing regressions
by Barend Gehrels 21 Jan '17

21 Jan '17

Hi, The regression matrix in develop of Boost.Geometry contains many new compilation failures due to: 1) : D:\t08\run\boost_root\boost/serialization/array.hpp(25) : error C2039: 'array' : is not a member of 'std' 2): ../boost/numeric/ublas/storage.hpp: In member function ???void boost::numeric::ublas::unbounded_array<T, ALLOC>::serialize(Archive&, unsigned int)???: ../boost/numeric/ublas/storage.hpp:331:18: error: ???make_array??? is not a member of ???boost::serialization??? ar & serialization::make_array(data_, s);and a The master is still OK. Can this be solved? Regards, Barend

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Boost Cmake Modules
by Paul Fultz II 20 Jan '17

20 Jan '17

Hi All, So I would like to start work with adding support for cmake to boost libraries. To make the boilerplate needed to write some of the cmake, I wrote BCM(Boost Cmake Modules), here: https://boost-cmake.github.io/bcm/doc/html/ Of course, the documentation is still a WIP. The core part is bcm_boost_package. So to write cmake for a library, you would just write something like this: bcm_boost_package(core VERSION 1.0 DEPENDS config ) It also provides a mechanism to add tests as well. My goal at first would be to update libraries on per-module level(one PR at a time). So to use cmake, the user wold build and install each library individually with cmake. Later, we can update the cmake modules to support superproject building(which may be necessary for libraries that have circular dependencies). Right now, there are no modules for building documentation. This can be added later, as well. So does anyone have any feedback on this setup? If you had ideas, or would like to help update boost libraries, contributions are welcome. Thanks, Paul

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Testing issues
by Belcourt, Kenneth 19 Jan '17

19 Jan '17

Hi, Tests seem to have stopped cycling, and I see this error in the nightly testing output: error: Cannot create link ../../../boost_root/boost/process.hpp to ../../../boost_root/libs/process/include/boost/process.hpp. error: Link previously defined to another file, ../../../boost_root/libs/proccess/include/boost/process.hpp. # Searching for "process_jam_log" in "/scratch/kbelco/boost_testing/boost_regression/stage/bin"... Traceback (most recent call last): File "run.py", line 71, in <module> runner(root) File "/scratch/kbelco/boost_testing/boost_regression_src/regression.py", line 287, in __init__ self.main() File "/scratch/kbelco/boost_testing/boost_regression_src/regression.py", line 624, in main getattr(self,action_m)() File "/scratch/kbelco/boost_testing/boost_regression_src/regression.py", line 581, in command_regression self.command_setup() File "/scratch/kbelco/boost_testing/boost_regression_src/regression.py", line 352, in command_setup self.build_if_needed(self.process_jam_log,self.pjl_toolset) File "/scratch/kbelco/boost_testing/boost_regression_src/regression.py", line 715, in build_if_needed tool[ 'build_path' ] = self.tool_path( tool ) File "/scratch/kbelco/boost_testing/boost_regression_src/regression.py", line 740, in tool_path , '\n'.join( [ name_or_spec[ 'path' ], build_dir ] ) Exception: Cannot find "process_jam_log" in any of the following locations: Does this problem look familiar to anyone? —- Noel

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[asio] doc format changed?
by Vinnie Falco 19 Jan '17

19 Jan '17

Why did the formatting for Boost.Asio documentation change from 1.61 to 1.63? Compare: http://www.boost.org/doc/libs/1_61_0/doc/html/boost_asio.html http://www.boost.org/doc/libs/1_63_0/doc/html/boost_asio.html This looks like it was unintended, and its screwing up search engines (try searching for "Boost Asio 1.63.0 Reference" -- Follow me on Github: https://github.com/vinniefalco

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[Interprocess] move semantics for intrusive_ptr
by Mikolaj Krzewicki 19 Jan '17

19 Jan '17

Dear all, would it be possible to add the rvalue operators to interprocess::intrusive_ptr akin to what is already available in "regular" boost::intrusive_ptr: // Move support #if !defined( BOOST_NO_CXX11_RVALUE_REFERENCES ) intrusive_ptr(intrusive_ptr && rhs) BOOST_NOEXCEPT : px( rhs.px ) { rhs.px = 0; } intrusive_ptr & operator=(intrusive_ptr && rhs) BOOST_NOEXCEPT { this_type( static_cast< intrusive_ptr && >( rhs ) ).swap(*this); return *this; } #endif many thanks, Mikolaj

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[outcome] "sea of noexcept, islands of throwing"
by Andrzej Krzemienski 18 Jan '17

18 Jan '17

Niall, I moved this to another thread, as I believe it is quite independent of the documentation review. I am trying to understand the concept of "sea of noexcept, islands of throwing", and its significance. First, is this programming technique the primary motivation for Boost.Outcome? In the docs, I only saw a small mention of it, but from your replies it looks like this is an important part of the library. But I might be wrong. This "sea and islands" are quite similar to what is described in P0364R0 ("Report on Exception Handling Lite (Disappointment) from SG14"). The authors argue that if the exception control flow is indicated explicitly, the compiler has a better chance of performing optimizations. I understand that your goal (with the Outcome library) is to offer something more modest, but implementable in C++. You are saying, that the C++ compiler can implement similar optimizations, provided that all the try-catch-throw flows are confined to one translation unit. Did I get it right? The authors of P0364R0 claim that in some business domains, like video games, if you encounter a failure to acquire resources, you might as well terminate the program. For this reason RAII is not really that important there: you want to shut down the app rather than clean up and continue. Is it also what you are saying? Do you also intend to support something like 'panic mode' in Rust? I do not know Rust, but I understand that this 'panic mode' is shut down the program but with resource cleanup. Sorry, my questions are quite random. But I am trying to understand the idea. Regards, &rzej;

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Generating Boost documentation with pandoc
by Vinícius dos Santos Oliveira 18 Jan '17

18 Jan '17

Has anyone tried to generate Boost-styled documentation using pandoc? I never fully liked PDF documentation because I never actually print documentation. However, a few weeks ago I got an ebook reader and I've been fascinated by the ePUB format. I'm using it to read even the IETF's RFCs and it's very pleasant. I'm using ePUB to read files even on my usual laptop. Anyway, I was wondering how nice would be to have an ePUB file containing the whole Boost documentation. pandoc has docbook support as one of its input formats and is capable of generating great ePUB output. -- Vinícius dos Santos Oliveira https://vinipsmaker.github.io/

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[outcome] Added LEWG expected<T, E> implementation, what about the tutorial?
by Niall Douglas 17 Jan '17

17 Jan '17

Quite a bit of feedback from here, from SG14 and from Reddit expressed disappointment that Outcome doesn't implement the LEWG expected<T, E>. basic_monad makes implementing a fully compliant expected<T, E> just a few hours of work, so I went ahead and added one today and you can see its reference docs at https://ned14.github.io/boost.outcome/group__expected.html. These are the known deviations from the LEWG proposal: * P0323R1 doesn't yet specify what will be done if you try accessing an expected which is valueless due to exception. We throw a bad_expected_access<void> in this situation as that seemed sensible. If the LEWG proposal decides on something different, this implementation will change to track the LEWG proposal. * unexpected_type<E> is implemented as an expected<void, E> and it lets the basic_monad machinery do the implicit conversion to some expected<T, E>. * Types T and E cannot be constructible into one another. * expected<T, E> defaults E to error_code_extended. If you don't like this, predefine the BOOST_OUTCOME_EXPECTED_DEFAULT_ERROR_TYPE macro. * The ordering operators are not implemented due to https://akrzemi1.wordpress.com/2014/12/02/a-gotcha-with-optional/ So now you get in Outcome expected<T, E>; option<T>, result<T> and outcome<T>. And the Expected implementation ought to be drop in compatible with any future C++ 20 standard. How would people prefer the Outcome tutorial to now go? Should it mention expected<T, E> at all? Or should it get its own tutorial page (which will look very similar to the tutorial for result<T>). Which order should they be in? Is expected<T, E> easier than outcomes or the other way round? Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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docs for hana broken on webpage (boost 1.63)
by Hans Dembinski 17 Jan '17

17 Jan '17

Hi, the current docs for Hana are still broken: http://www.boost.org/doc/libs/1_63_0/libs/hana/doc/html/index.html yields "404 Not Found". Best regards, Hans

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[function] Problem with simple pointer to function
by Fu ji 17 Jan '17

17 Jan '17

Hello all, I have a problem with boost::function, when I try to assign function to pointer I have a crash. It is simple void function(); boost::function <void (void)> m_Wakeup; and the code where crush occurs looks like: Wakeup = &function; Here is also the dump: Program terminated with signal 6, Aborted. *#0 0x03c4a092 in _dl_start () from /lib/ld-linux.so.2* *#0 0x03c4a092 in _dl_start () from /lib/ld-linux.so.2* *#1 0x03d0eca5 in raise () from /opt/vmware/cimpdk-6.0.0-2768847/debug/build-3825889/lib/libc.so.6* *#2 0x03d104e3 in abort () from /opt/vmware/cimpdk-6.0.0-2768847/debug/build-3825889/lib/libc.so.6* *#3 0x03ca2aec in handleSigSegv () from /opt/vmware/cimpdk-6.0.0-2768847/debug/build-3825889/usr/lib/libsfcBrokerCore.so.0* *#4 0x00310002 in ?? ()* *#5 0x025c060a in move_assign () at /workspace/raid0/src/boost/function/function_template.hpp:998* *#6 swap () at /workspace/raid0/src/boost/function/function_template.hpp:870* *#7 operator=<void (*)()> () at /workspace/raid0/src/boost/function/function_template.hpp:1126* *#8 create_interface () at /workspace/raid0/src/CppWrapper.cpp:298* Do anyone have a clue what was wrong ? Best regards

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Interest in updated expression template library?
by Zach Laine 17 Jan '17

17 Jan '17

I'm trying to gauge interest in submitting a library to the review queue, It's an expression template library called Yap using C++14 and C++17 features, built on top of Hana. It does not work quite the same as Proto, though of course it covers the same problem domain. My goal for the library was to cover the Proto functionality (while allowing the user to write less code than she would have had to with Proto) plus more functionality made easier by the new language features. In the examples you will find nearly all of the Proto examples reproduced, each in a-bit-less to dramatically-less code. The only Proto examples that were left out were ones that are now trivial using Yap due to differences in design. Online docs: https://tzlaine.github.io/yap GiHub page: https://github.com/tzlaine/yap Zach

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BGL Algo Contribution
by Robert R. McCune 17 Jan '17

17 Jan '17

Hello, I'd like to contribute to the Boost Graph Library I've written code for Lexicographic Breadth-First Search (LexBFS) How may I best contribute? Thanks, Ryan

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Re: [boost] Boost 1.64 release date
by Rene Rivera 16 Jan '17

16 Jan '17

On Tue, Jan 10, 2017 at 4:16 AM, Raffi Enficiaud < raffi.enficiaud(a)mines-paris.org> wrote: > Dear all, > > I would like to know in advance (approximately) the release date of 1.64. > > Would it be possible to date of the next release at each new release? > Release Dates Spring release on the second Wednesday of April. Summer release on the second Wednesday of August. Fall/Winter release on the second Wednesday of December. <https://svn.boost.org/trac/boost/wiki/ReleaseSchedule> -- -- 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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[SmartPtr] alternative to enable_shared_from_this
by Roberto Hinz 16 Jan '17

16 Jan '17

Dear Boost Community, I've been following this list for a time with the desire of contributing to Boost. It seems to me a good idea to start with small and easy to review proposals, before attempting anything big. So my first shot is shared_handle class, an alternative to enable_shared_from_this that doesn't suffer from multiple inheritance issues. It also provides the capability of instantiating a shared_ptr to a member object. doc: https://robhz786.github.io/smart_ptr/shared_handle.html source: https://github.com/boostorg/smart_ptr/compare/develop... robhz786:develop Unfortunately, the implementation produces at least one regression: clang 3.1 crashes when it compiles cpp11_pointer_cast_test.cpp with -std=c++11. There may be others since I couldn't test in all compilers used in the regression tests. Nevertheless, is there any interest? Kind regards, Roberto Hinz

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