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[utility] Re: Massive test failures due to ambiguous namespace
by Rene Rivera 23 Feb '16

23 Feb '16

On Tue, Feb 23, 2016 at 1:31 PM, Markus Trippelsdorf <markus(a)trippelsdorf.de > wrote: > http://www.boost.org/development/tests/develop/developer/summary.html > show many "fails" due to: > > In file included from ../libs/chrono/src/process_cpu_clocks.cpp:17: > In file included from > ../boost/chrono/detail/inlined/process_cpu_clocks.hpp:19: > In file included from ../boost/chrono/process_cpu_clocks.hpp:22: > In file included from ../boost/chrono/detail/system.hpp:12: > ../boost/system/error_code.hpp:431:15: error: 'detail' is not a class, > namespace, or scoped enumeration > { return *detail::throws(); } > ^ > ../boost/system/error_code.hpp:431:15: error: reference to 'detail' is > ambiguous > { return *detail::throws(); } > ^ > ../boost/system/error_code.hpp:421:13: note: candidate found by name > lookup is 'boost::detail' > namespace detail { inline system::error_code * throws() { return 0; } } > ^ > ../boost/operators.hpp:658:11: note: candidate found by name lookup is > 'boost::operators_impl::detail' > namespace detail > ^ > 2 errors generated. > Also.. This is affecting general building of release packages. First time it showed up was with this superproject update < https://travis-ci.org/boostorg/boost/jobs/111041426>. 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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Massive test failures due to ambiguous namespace
by Markus Trippelsdorf 23 Feb '16

23 Feb '16

http://www.boost.org/development/tests/develop/developer/summary.html show many "fails" due to: In file included from ../libs/chrono/src/process_cpu_clocks.cpp:17: In file included from ../boost/chrono/detail/inlined/process_cpu_clocks.hpp:19: In file included from ../boost/chrono/process_cpu_clocks.hpp:22: In file included from ../boost/chrono/detail/system.hpp:12: ../boost/system/error_code.hpp:431:15: error: 'detail' is not a class, namespace, or scoped enumeration { return *detail::throws(); } ^ ../boost/system/error_code.hpp:431:15: error: reference to 'detail' is ambiguous { return *detail::throws(); } ^ ../boost/system/error_code.hpp:421:13: note: candidate found by name lookup is 'boost::detail' namespace detail { inline system::error_code * throws() { return 0; } } ^ ../boost/operators.hpp:658:11: note: candidate found by name lookup is 'boost::operators_impl::detail' namespace detail ^ 2 errors generated. -- Markus

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boost::container::set insert range bug
by Han Wang 23 Feb '16

23 Feb '16

Hi, Let's say we have some simple code here. boost::container::set<int> s; boost::container::set<int> const sp; s.insert(boost::begin(sp), boost::end(sp)); This insert call will cause "ambiguous call to overloaded function". Best regards, Han

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GSoC Project Proposal - Boost Document Library Extensions
by Anurag Ghosh 23 Feb '16

23 Feb '16

Hello everyone! I wished to propose continue working on the Boost Document Library as a part of the Google Summer of Code 2016, and would like to work on the following things this summer on the library which was started last summer - 1. Integrating Basic Chart Support. 2. Writing comparators for the cells. (Cells are heterogeneous in nature, similar to Boost.Variant) 3. Making cell class have the behavior of a reference to the document's cell. 4. Basic formatting options for cell contents. Kindly make appropriate suggestions to my proposal. The aim of the proposal is to make it a Boost-Ready library. I would remind everyone that the library in its current state has basic spreadsheet functionality like opening, closing and exporting documents, sheet operations and cell,row,column (iterators) operations for Linux and Windows through wrappers over LibreOffice and Microsoft Office API's. ( https://github.com/BoostGSoC15/boost-document) I have been inactive for sometime, but I hope to improve test coverage before March and fix some other issues. Thanks Anurag Ghosh researchweb.iiit.ac.in/~anurag.ghosh

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[Core] BOOST_TRY/BOOST_CATCH
by Chris Glover 22 Feb '16

22 Feb '16

Hi, I ran into a problem when trying to use BOOST_TRY/BOOST_CATCH to add no-exception support to property tree. Here's an example of the original code; try { write_ini(stream, pt, flags); } catch (ini_parser_error &e) { BOOST_PROPERTY_TREE_THROW(ini_parser_error( e.message(), filename, e.line())); } I converted this code to use the macros from core/no_exception_support.hpp *BOOST_TRY *{ write_ini(stream, pt, flags); } *BOOST_CATCH *(ini_parser_error &e) { BOOST_PROPERTY_TREE_THROW(ini_parser_error( e.message(), filename, e.line())); } *BOOST_CATCH_END* The issue is that now the exception, ini_parser_error& e, is not defined when I compile with exceptions off. I solved this by adding a local instance of ini_parser_error above the try block *ini_parser_error e("", "", 0);* BOOST_TRY { write_ini(stream, pt, flags); } BOOST_CATCH (ini_parser_error &e) { BOOST_PROPERTY_TREE_THROW(ini_parser_error( e.message(), filename, e.line())); } BOOST_CATCH_END This is a little gross, but it's not too bad and I was expecting the variable to be optimized away. But it isn't -- instantiating that exception on the stack is very clearly generating instructions on VS2015 and GCC 5.3. While this is not a huge deal, I don't like it so one way I can think to fix this is to conditionally compile out the catch block, but that defeats the purpose of the macros in the first place. BOOST_TRY { write_ini(stream, pt, flags); } BOOST_CATCH (ini_parser_error &e) { *#ifdef BOOST_NO_EXCEPTIONS* BOOST_PROPERTY_TREE_THROW(ini_parser_error( e.message(), filename, e.line())); *#endif* } BOOST_CATCH_END Then I thought maybe I can declval a fake 'e' in the else block by redefining the macros as follows; #ifndef BOOST_NO_EXCEPTIONS #define BOOST_TRY { try { #define BOOST_CATCH(type, var) } catch(type var) { #define BOOST_CATCH_END } } #else #define BOOST_TRY { if(true) { #define BOOST_CATCH(type, var) } else if(false) { type var = boost::declval<type>(); #define BOOST_CATCH_END } } #endif This is working, but is possibly undefined behaviour. Does anyone have thoughts on that? It also requires splitting up the type from the variable name. The next step to this would be to add a third parameter for some constructor args so we can just create an exception object directly. Something like: #define BOOST_CATCH(exception_type, var, args) } else if(false) { boost::decay<exception_type>::type var args; So now the original code would look like this: BOOST_TRY { write_ini(stream, pt, flags); } BOOST_CATCH (ini_parser_error&, e, ("", "", 0)) { BOOST_PROPERTY_TREE_THROW(ini_parser_error( e.message(), filename, e.line())); } BOOST_CATCH_END This is starting to look a little nasty to me so I'm wondering if anyone has any thoughts on this? Should I stop worrying about it and just use the #ifdef? The reality is that I work in an environment without exceptions and we hit these things from time to time so I'd like to fix up as many as possible. Thanks, -- chris

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media file error
by Rainer Deyke 21 Feb '16

21 Feb '16

In "CDs/Presumed Guilty Compilation": "Beyond Dwan - Need.mp3" -> "Beyond Dawn - Need.mp3" -- Rainer Deyke (rainerd(a)eldwood.com)

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What's wrong with this benchmark
by Benedek Thaler 20 Feb '16

20 Feb '16

Dear Boost, In a previous mail, I introduced a container library, `double_ended`. This library has benchmarks [0]. However, the benchmarks show unexpected results. This is what I do [1]: - compile program using G++ 5.3, -O2 - remove CPU0 from kernel scheduler pool (isolcpu=0 boot flag) - disable CPU scaling - pin benchmark thread to CPU0 - in the test, create a vector - reserve memory for 1M unsigned - write a byte to each page reserved, to warm up the page table - get TSC value (machine has constant_tsc flag) - insert 1M unsigned value - get TSC value again, subtract previous value - repeat test 25 times, average results I do this with 3 containers: std::vector, boost::container::vector and double_ended::devector. While the latter two produces almost equivalent results, std::vector seriously falls behind. - No reallocation happens between the TSC sampling - Test order doesn't matter: every order produces the same results - Container size or sample count doesn't matter, same results. - The deviations of individual measures of each container is small, the performance is consistent. - I compared the produced ASM of std::vector and double_ended::devector, they are very similar, almost the same instructions in different order [2]. What do I miss here? Thanks, Benedek [0]: http://erenon.hu/double_ended/double_ended/benchmarks.html [1]: https://github.com/erenon/double_ended/blob/master/benchmark/push_back.cpp [2]: http://pastebin.com/tUL54i9f

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[RFC] C++ apparently lacks a mechanism for locking ranges of a shared resource
by Raphael S Carvalho 20 Feb '16

20 Feb '16

I am very sorry if this topic is unrelated to the topics covered by this mailing list. While developing a small project which consists of exporting a blockv device via network (if you are curious: https://github.com/raphaelsc/blockv) there was the need to lock a range of a shared resource, such as a file. I searched for resources coming from C++ standard library and boost library, but I wasn't able to find anything that would fit my needs. Am I missing something? Anyway, I ended up implementing my own range locking mechanism. The implementation is quite simple, feel free to look it at: https://github.com/raphaelsc/byte-range-lock-cpp/blob/master/range_lock.hh (I made my best effort to document it well) Is there any chance that something like range_lock will be made available in the next versions of boost library? Thank you very much for reading this, Raphael Carvalho

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Re: [boost] [optional] optional(Expr&&) is insufficiently constrained
by Andrzej Krzemienski 19 Feb '16

19 Feb '16

2016-02-18 23:03 GMT+01:00 Stephan T. Lavavej <stl(a)exchange.microsoft.com>: > Hi, > > A user reported a bug (VSO#191303/Connect#2351203, see [1]) using > Boost.Optional with MSVC 2015 Update 2. The original test case involved a > minor bug in VC's tuple, which I'll look into fixing in the future > (specifically, N-tuples recursively construct (N - 1)-tuples, in a way > that's visible to overload resolution). However, there is also a bug in > boost::optional. > Hi, I have created a ticket abut this problem: https://svn.boost.org/trac/boost/ticket/12002 Frankly, I do not know how to implement it in a portable way (considering older compilers) without type trait boost::is_constructible. I am currently blocked on it: https://svn.boost.org/trac/boost/ticket/12003. As an aside, the "prevent_binding" stuff should probably be expressed as a > SFINAE constraint, not a static_assert. > About this remark, I am not sure. I understand that you want the constructors to be SFINAE-friendly, but at the same time I would loose the opportunity to convey a text message to the user-programmers, as to what the problem is. Now I do it with the static_assert. I wish I had the feature "delete for a reason" Optional::Optional(R&&r) = delete("because it would cause..."); Regards, &rzej

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[iterator] function_output_iterator constructed from a lambda function is not assignable
by Mikhail Matrosov 19 Feb '16

19 Feb '16

Consider the following code snippet: auto f = [](int x) { std::cout << x; };auto it = boost::make_function_output_iterator(f);decltype(it) it2 = it; // Ok, copied it2 = it; // Does not compile, cannot assign! The problem is, function_output_iterator constructed in this way is not assignable, and thus does not satisfy the Iterator <http://en.cppreference.com/w/cpp/concept/Iterator> concept, which requires type to be CopyAssignable <http://en.cppreference.com/w/cpp/concept/CopyAssignable>. This is not a bug, since boost Function Output Iterator documentation <http://www.boost.org/doc/libs/1_60_0/libs/iterator/doc/function_output_iter…> clearly says <http://www.boost.org/doc/libs/1_60_0/libs/iterator/doc/function_output_iter…> : UnaryFunction must be Assignable and Copy Constructible. While assignment operator of a lambda function <http://en.cppreference.com/w/cpp/language/lambda> is deleted: ClosureType& operator=(const ClosureType&) = delete; So this behaviour is technically correct, but for me is somewhat unexpected. I think it is a perfectly reasonable desire to construct function_output_iterator given a closure produced by lambda function. It seems inconvenient to me why this use case causes a problem. Can you suggest a workaround for this situation? Or maybe a way of improving function_output_iterator to overcome this issue? Personally, I came up with a trick to fix this in a situation, when I'm sure iterator and its copies won't outlive the closure object. In this case we may wrap closure with std::ref: auto it = boost::make_function_output_iterator(std::ref(f)); This works quite fine, but obviously is not always possible. Another options is to store closure in std::function: std::function<void(int)> f = [](int x) { std::cout << x; }; This also works fine and is possible in most contexts, but causes related overheads. See also: http://stackoverflow.com/q/35392919/261217 ----- Best regards, Mikhail Matrosov

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