February 2014 - Boost - lists.preview.boost.org

[git] Near future.. How do we deal with git-native libraries?
by Rene Rivera 05 Apr '14

05 Apr '14

As the owner of the Predef library which exists originally in github and not svn.. I'm wondering about some things for the near future (as in this coming week): 1. Where will the git repo live for a library? Will the repo need to stay in the boostorg organization? Or is it possible/desirable to use the existing repo that's part of my user account? 2. I notice that there's a ".gitattributes" file in the svn imported version of the Predef repo. Will I need to add that file to my actual Predef git repo? And if so, is there a single canonical version of that file I should use? And a followup.. In the future if that file changes, does it need to change for all repos consistently? Rene. -- -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org - grafik/redshift-software.com -- 102708583/icq - grafikrobot/aim - grafikrobot/yahoo

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[asio] Bug: Handlers execute on the wrong strand.
by Greg Barron 04 Apr '14

04 Apr '14

Hi All, I would like to refer you to this bug report: https://svn.boost.org/trac/boost/ticket/9203 I won't paste the full contents of the bug report into this message. The executive summary is that the allocation algorithm for the implementation of asio::strand can and does allocate the implementation of an existing strand to strands that are subsequently allocated. This can have the effect that handlers wrapped in strand (b) will actually be executed on strand (a). I consider this to be a bug but if there is something that I'm misunderstanding about the operation of strands it would be great if you could help me clear it up. If the consensus is that this is a bug, what are the chances for it to be included in the 1.56 release? It is probably too late to be included in the 1.55 release. I've implemented a work around which could only be described as a hack and would be embarrassed to show it to anybody. But it gets me over my hump :). Thanks! -- Greg

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Post-git forking process
by Sohail Somani 29 Mar '14

29 Mar '14

Hey all, Often, I find bugs in Boost that I need to patch manually before the next release. What I used to do before was keep a copy of Boost in my source tree which made this easier: just patch it directly. This made it easy to modify, but annoying to post patches and honestly, they just got lost most of the time. With Git, it should become easier to contribute said patches as well as pull in whichever particular changes I need. However when I attempted such a fork recently, I was a bit lost. As I understood it, the process should have been: 1. Create a fork of https://github.com/boostorg/boost and use this fork in my project 2. Create a fork of the library/libraries I wanted to patch 3. Update the submodules in my boostorg/boost fork to point to my forked libraries 4. Post a pull request for the respective libraries. Once the changes have been accepted, point back to the official boostorg repo I failed terribly, no doubt due to PEBKAC. Is there a chance that someone could write a tutorial or a how-to guide for the recommended process of forking Boost with Git? The main thing I need is the ability to have a patched version of Boost that I can use while the patches are being reviewed/accepted/rejected. Thanks, Sohail

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[algorithm] Test failure in C++14
by Ben Pope 25 Mar '14

25 Mar '14

"clang++-3.4" -c -x c++ -std=c++1y -stdlib=libc++ -O0 -g -fno-inline -Wall -g -fPIC -DBOOST_ALL_NO_LIB=1 -DBOOST_TEST_DYN_LINK=1 -DBOOST_TEST_NO_AUTO_LINK=1 -I".." -o "/home/ben/development/boost/test/build/results/boost/bin.v2/libs/algorithm/test/is_permutation_test1.test/clang-linux-3.4~c14_libc++/debug/is_permutation_test1.o" "../libs/algorithm/test/is_permutation_test1.cpp" In file included from ../libs/algorithm/test/is_permutation_test1.cpp:13: ../boost/algorithm/cxx11/is_permutation.hpp:178:6: error: declaration conflicts with target of using declaration already in scope bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1, ^ /usr/include/c++/v1/algorithm:1374:1: note: target of using declaration is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, ^ ../boost/algorithm/cxx11/is_permutation.hpp:104:12: note: using declaration using std::is_permutation; // Section 25.2.12 ^ ../boost/algorithm/cxx11/is_permutation.hpp:205:6: error: declaration conflicts with target of using declaration already in scope bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1, ^ /usr/include/c++/v1/algorithm:1361:1: note: target of using declaration is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, ^ ../boost/algorithm/cxx11/is_permutation.hpp:104:12: note: using declaration using std::is_permutation; // Section 25.2.12 ^ 2 errors generated. I haven't looked in detail, but it looks like those two overloads were added in C++14 and need guarding with a suitable #if __cplusplus >= C++1Y_version_here Ben

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Library metadata
by Daniel James 17 Mar '14

17 Mar '14

Hi, I'm starting to add metadata to modules for updating the website, and hopefully other uses in the future. I added the metadata to Boost.Unordered and Boost.Functional to give you an idea of what this will look like: https://github.com/boostorg/functional/tree/develop/meta https://github.com/boostorg/unordered/tree/develop/meta You can see several libraries listed in the Boost.Functional file. I'll write some documentation soon, but it should be fairly easy to understand. I basically took what was in the website library list and split it up into modules. Quick summary of the fields: key - Used to be the website to identify each library. Don't change it, or the website will think it's a new library. boost-version - The version in which the library was released. name - The name of the library. authors - The authors of the library - will probably add a 'maintainers' field later. description - Library description - this is used in the library list, so keep it short. std-proposal - Is the library proposed for the standard. std-tr1 - Is the library part of TR1. category - The categories the library belongs to. one element for each category. The documentation will include a list of available categories. documentation - Path to the documentation. The documentation field is optional. If it isn't included, it'll use the default path: /libs/module-name/. If it is included, relative paths are resolved relative to the module directory, absolute paths from boost root - although I'd suggest you always use a path within the module, and if there's only a single library in a module, use the default path. This isn't the final format - I think the standards status fields could do with an overhaul to support C++11 etc. You also don't need to write the initial files yourself, I'll generate them and create pull requests once this is settled. Let me know what you think. thanks, Daniel

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[GSoC] pipelines questions
by Thaler Benedek 06 Mar '14

06 Mar '14

Hi, I'm interested in the Boost.Pipelines proposal of GSoC 2014. [0] I'd like to ask the stakeholder (Vicente J. Botet Escriba ?) the following: * Is this supposed to be built from scratch or rather to be some kind of improvement over the already existing google implementation? [1] * If the former is true, should be n3534 [2] considered as a strict requirement or as a vague suggestion? * If the later is true, which features should be the main distinctive ones? I think about things like using Boost libraries (e.g: Boost.Atomic) instead of custom solutions, cross platform support, comply to Boost coding standard, etc. Are there any areas of improvement identified in the reference implementation? * I understand it might take quite a long time for a proposal to make it to Boost, therefore it's not a requirement. Is there any objective milestone that a successful project should reach anyway? Thanks, Benedek [0]: https://svn.boost.org/trac/boost/wiki/SoC2014#Boost.Pipelines [1]: https://code.google.com/p/google-concurrency-library/source/browse/include/… [2]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3534.html#Proposal

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[signals2] Test failure in C++11 (trivial fix for incorrect usage of boost::optional)
by Ben Pope 06 Mar '14

06 Mar '14

I have the following errors: "clang++-3.4" -c -x c++ -std=c++11 -stdlib=libc++ -O0 -g -fno-inline -Wall -g -DBOOST_ALL_NO_LIB=1 -DBOOST_TEST_NO_AUTO_LINK=1 -I".." -o "/home/ben/development/boost/test/build/results/boost/bin.v2/libs/signals2/test/signal_test.test/clang-linux-3.4~c11_libc++/debug/link-static/signal_test.o" "../libs/signals2/test/signal_test.cpp" ../libs/signals2/test/signal_test.cpp:32:16: error: invalid operands to binary expression ('boost::optional<int>' and 'int') if(max == false) max = *first; ~~~ ^ ~~~~~ "clang++-3.4" -c -x c++ -std=c++11 -stdlib=libc++ -O0 -g -fno-inline -Wall -g -DBOOST_ALL_NO_LIB=1 -DBOOST_TEST_NO_AUTO_LINK=1 -I".." -o "/home/ben/development/boost/test/build/results/boost/bin.v2/libs/signals2/test/track_test.test/clang-linux-3.4~c11_libc++/debug/link-static/track_test.o" "../libs/signals2/test/track_test.cpp" ../libs/signals2/test/track_test.cpp:36:14: error: invalid operands to binary expression ('boost::optional<int>' and 'int') if(max == false) Richard smith explains the problem here: http://llvm.org/bugs/show_bug.cgi?id=18180#4 "OK, I see what's happening -- in Clang 3.3 and GCC 4.8, 'false' is being treated as a null pointer constant. boost::optional implicitly converts to an "unspecified-bool-type" that happens to be a pointer-to-member type, and thus can be compared against a null pointer constant via the built-in operator!=(pointer-to-member, pointer-to-member) overload. In C++11 onwards, 'false' isn't a null pointer constant any more, so this comparison is no longer valid. Clang 3.3 and GCC 4.8 don't implement that rule; Clang 3.4 does." The trivial fix is to change the if statements at: ../libs/signals2/test/signal_test.cpp:32:16: ../libs/signals2/test/track_test.cpp:36:14: to if(!max) rather than if(max == false). Ben

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libcpp.hpp always defines BOOST_NO_CXX11_HDR_ATOMIC
by Peter Dimov 05 Mar '14

05 Mar '14

The libc++ config header, libcpp.hpp, always defines BOOST_NO_CXX11_HDR_ATOMIC, but the libc++ that - I presume - ships with "Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)" appears to have a functional <atomic>.

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Formal review request: Boost.Mixin
by Borislav Stanimirov 05 Mar '14

05 Mar '14

Hello, I'd like to request a formal review of Boost.Mixin. Code is here: https://github.com/iboB/boost.mixin Documentation is here: http://ibob.github.io/boost.mixin/ In short, the library allows you to dynamically compose and mutate polymorphic types from existing C++ classes. Thanks, -- Borislav

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DRYing BOOST_FUSION_ADAPT_STRUCT with decltype/Boost.TypeOf ?
by Damien Buhl 05 Mar '14

05 Mar '14

Hi dear Boost Fusion developers, I was asking myself if there were already plan to improve BOOST_FUSION_ADAPT_STRUCT to benefit from C++11 features like decltype ? This would be interesting to avoid the risk encountered that the types definitions can get out-of-sync. And would avoid typing type declarations twice. Currently there is BOOST_FUSION_DEFINE_STRUCT to avoid repeating the type information for each field. However this is something that makes most developer I know unhappy, as it obliges to modify the readable C++ aggregate types definition (i.e. Could be public headers) with this macro. Then there is the nice choice of BOOST_FUSION_ADAPT_STRUCT which obliges retyping the type and adds the risk that some field type information could get out-of-sync between the struct definition and the BOOST_FUSION_ADAPT_STRUCT listing. I think it would be valuable to add macros that would enable to select the fields that we want to adapt to a Random Access Sequence without requiring to repeat the type information. I would find more comfortable to write the example provided here http://www.boost.org/doc/libs/1_55_0/libs/fusion/doc/html/fusion/adapted/ad… as follow : namespace demo { struct employee { std::string name; int age; }; } // demo::employee is now a Fusion sequence BOOST_FUSION_ADAPT_STRUCT_EXT( demo::employee, (name) (age)) And a naïve implementation of BOOST_FUSION_ADAPT_STRUCT_EXT could be: #include <boost/typeof/typeof.hpp> #include <boost/fusion/include/adapt_struct.hpp> #include <boost/preprocessor/seq/for_each.hpp> #define ATTRIBUTE_DEFINITION(r, data, elem) \ (BOOST_TYPEOF(data::elem), elem) \ #define BOOST_FUSION_ADAPT_STRUCT_EXT(NAME, ATTRIBUTES) \ BOOST_FUSION_ADAPT_STRUCT(NAME, \ BOOST_PP_SEQ_FOR_EACH(ATTRIBUTE_DEFINITION, NAME, ATTRIBUTES)) #endif The same could certainly be achieved for BOOST_FUSION_ADAPT_TPL_STRUCT, while I didn't check. Thanks for the really great job done in Boost.Fusion. Cheers, -- Damien Buhl alias daminetreg

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