July 2013 - Boost - lists.boost.org

[multimethods] Proposal: Open Multi-Methods
by Jean-Louis Leroy 01 Sep '13

01 Sep '13

Hi, I am working on library that pretty much implements what Pirkelbauer, Solodkyy and Stroustrup describe in their paper "Open Multi-Methods for C++" - although there are some divergences. I have posted it on GitHub: https://github.com/jll63/multimethods. Please examine the files in the "examples" directory to get an idea of how to use it. Salient features are: * syntax: is relatively uncluttered. There are no limitations on the number of virtual arguments. Virtual and non-virtual arguments can be arbitrarily mixed. Multiple inheritance is supported, with some limitations - see below. * speed: close to a virtual function call when the hierarchies involved in the virtual arguments collaborate with the library. Calling a method that does nothing, with a single virtual argument in a single inheritance hierarchy is 33% slower than the equivalent virtual function call. The difference becomes unnoticeable if the functions perform a few simple maths operations. See tests/benchmarks.cpp. * size: the dispatch table is constructed in terms of class groups. This results, most of the time, in a table devoid of redundancies. The size is bounded by the product of the number of specializers - not classes - in each dimension. * support for "foreign" class hierarchies: the library can be used without modifications to existing classes, at the cost of lower performance. Collaborating and foreign arguments can be freely mixed. Performance is still quite good, see the benchmarks. * next: a pointer to the next most specialized method is available inside method specializations - see examples/next.cpp. Alternatively, it is possible to call a specialization directly. Current limitations are: * restrictions on hierarchy: the classes involved in a method call must have a single root. Repeated inheritance is not supported. Multiple inheritance is supported, provided that the two conditions above are respected. * no overloading: multi-methods are implemented as constexpr function objects. This does not allow for overloading. This restriction can be easily side-stepped by wrapping multi-methods with different names in a set of overloaded functions. I know how to make multi-methods functions instead of objects, at the cost of a slightly less nice syntax for specializers. This is open to discussion. Besides, the library differs from Stroustrup et al's paper on the following points: * a specializer specializes only one multi-method: what would "next" mean otherwise? What would its static type be? * pure multi-methods are allowed: if called, an exception is thrown. This seems a better choice given that most of the time the declared virtual arguments will be abstract classes anyway. The library is essentially feature complete (if anything ever is). I am now going to work on the documentation, a build system, some clean up and compatibility (I tested it only with g++ 4.7.2 only so far). Is there interest in the Boost community for this stuff? If yes, I will adapt it to the guidelines and submit it for formal review. Of course, suggestions are welcome. Thank you for your time, Jean-Louis Leroy

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[type_triats] [move] is_copy_constructible<T> trait
by Antony Polukhin 26 Aug '13

26 Aug '13

Hi, I have an implementation of is_copy_constructible<T> trait. It works great with C++11, in C++03 it detects constructors assuming that if type is derived from boost::noncopyable or uses BOOST_MOVABLE_BUT_NOT_COPYABLE macro - it has no copy constructor. Questions are: * May I add that trait to trunk version of Boost.TypeTraits (with documentation and tests, as usual)? * May I or Boost.Move maintainer apply this patch to BOOST_MOVE_IMPL_NO_COPY_CTOR_OR_ASSIGN in boost/move/core.hpp : #ifdef BOOST_NO_CXX11_DELETED_FUNCTIONS #define BOOST_MOVE_IMPL_NO_COPY_CTOR_OR_ASSIGN(TYPE) \ private:\ TYPE(TYPE &);\ TYPE& operator=(TYPE &);\ + public: \ + typedef int boost_move_no_copy_constructor_or_assign; \ + private: \ // #else Why do I need this trait? Well, it allows to implement move_if_noexcept() that is required for circular_buffer and possibly for other containers. -- Best regards, Antony Polukhin

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Pre-build MSVC Boost binaries
by Fredrik Orderud 13 Aug '13

13 Aug '13

Over the last year, I've set up a small SourceForge "WinBin" project [1] for distributing Microsoft Windows binaries for Boost (and some other projects). The repository is sorted by Boost version, compiler version and shared vs. static linking. Each file archive contains pre-build boost in debug/release for both 32/64-bit, following a include/lib[64]/bin[64] folder structure. There also seems to be some other sources for pre-built boost around (e.g. https://sourceforge.net/projects/boost/files/boost-binaries/ and http://boost.teeks99.com/bin/) However, these do not seem to provide boost built for both static and shared linking. Also, they do not appear to adhere to the "quasi standard" include/lib[64]/bin[64] folder naming convention used by many libraries. Finally, they seem to lack information on which version of python (and possibly other 3rd party SW) they are compiled against. Therefore, I decided to set up my own boost-binaries webpage. Please let me know if you might be interested in either improving the "WinBin" project, or somehow joining forces to merge the various sources of Boost binaries into a single, more "authoritative" repository. I would be more than happy to shut WinBin down if "similar enough" binaries can be downloaded elsewhere. Thanks in advance, Fredrik Orderud [1] https://sourceforge.net/projects/winbin/files/boost/

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Line endings fixes
by Vitaly Budovski 13 Aug '13

13 Aug '13

Hi, Please see the attached files. boost_endings1.patch just sets some of the cpp and other text files to have file endings consistent with the rest of the repository. boost_endings2.patch may be controversial as it does the same but for the svg files. Some of them are marked as text, others as binary. It's a real mess. Most of the svg files are generated from other sources so should probably be omitted from the repository and simply regenerated when docs are built. Came across these issues when checking out the modularised boost git repository. Regards, Vitaly

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[mixin] New library reminder
by Borislav Stanimirov 11 Aug '13

11 Aug '13

Hello, Some of you might remember the previous discussion on the subject (archived here: http://lists.boost.org/Archives/boost/2013/01/200598.php) Anyway, in short, I'm developing a library with the intention to formally submit it to Boost by the end of the year. You can find it here: https://github.com/iboB/boost.mixin The latest news about it is that I think that the library's features for the formal submission are done and all that's left are minor tweaks, bug fixes, tests, examples, and, most importantly, a complete documentation. In the meantime, I again invite you all to check it out. Any comments, suggestions, and questions will be greatly appreciated. Thanks, -- Borislav

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Boost 1.54 build problem: --without-context not honoured?
by Steve M. Robbins 11 Aug '13

11 Aug '13

Hi, I'm digging into a build problem and noticed that even though I specify "./bjam --without-context", Boost.Context is still built! The bjam configuration output states that Context is not to be built: Component configuration: - atomic : building - chrono : building - context : not building - coroutine : building - date_time : building - exception : building But it is built nonetheless. This causes a build failure for architectures which are not supported; see build log [1]. Compare that to the build for 1.53 [2] which works fine. I've diffed the libs/context directory between 1.53 and 1.54 and nothing jumps out at me as the cause. Has anyone noticed and fixed this already? Thanks, -Steve [1] https://buildd.debian.org/status/fetch.php?pkg=boost1.54&arch=ia64&ver=1.54… [2] https://buildd.debian.org/status/fetch.php?pkg=boost1.53&arch=ia64&ver=1.53…

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[boost/spirit] numeric policy
by Brian Schrom 07 Aug '13

07 Aug '13

I've had the case where I needed to retain formatting information for a number (general, fixed, scientific) and was nicely accomplished by extending the policy, but needed to have a begin_parse() and end_parse() for the policy to be complete. It seems that it makes some sense or is this accomplished another way? Maybe something to consider for policies in general? Index: qi/numeric/real_policies.hpp =================================================================== --- qi/numeric/real_policies.hpp (revision 85166) +++ qi/numeric/real_policies.hpp (working copy) @@ -28,6 +28,18 @@ static bool const allow_trailing_dot = true; static bool const expect_dot = false; + template <typename Attribute> + static void + begin_parse(Attribute& attr_) + { + } + + template <typename Attribute> + static void + end_parse(Attribute& attr_,bool /* result */) + { + } + template <typename Iterator> static bool parse_sign(Iterator& /*first*/, Iterator const& /*last*/) Index: qi/numeric/detail/real_impl.hpp =================================================================== --- qi/numeric/detail/real_impl.hpp (revision 85166) +++ qi/numeric/detail/real_impl.hpp (working copy) @@ -133,6 +133,7 @@ parse(Iterator& first, Iterator const& last, Attribute& attr, RealPolicies const& p) { + p.begin_parse(attr); if (first == last) return false; Iterator save = first; @@ -257,6 +258,7 @@ // If we got a negative sign, negate the number traits::assign_to(traits::negate(neg, n), attr); + p.end_parse(attr, true); // maybe this should return a bool and be the return value? // Success!!! return true; }

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[intrusive] Compilation problem with gcc 4.7
by Hartmut Kaiser 07 Aug '13

07 Aug '13

In code which compiled just fine I'm now seeing: In file included from /opt/boost/trunk-debug/boost/intrusive/slist_hook.hpp:24:0, from /opt/boost/trunk-debug/boost/intrusive/slist.hpp:21, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/lcos/local/mu tex.hpp:23, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/runtime/compo nents/server/wrapper_heap.hpp:20, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/runtime/compo nents/server/managed_component_base.hpp:13, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/lcos/base_lco .hpp:12, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/lcos/base_lco _with_value.hpp:11, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/performance_c ounters/counters.hpp:12, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/runtime/compo nents/server/runtime_support.hpp:32, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/hpx/runtime.hpp:1 2, from /opt/buildbot/slave/hpx_gcc47_x8664_boosttrunk_debug/build/src/hpx_main.cpp: 7: /opt/boost/trunk-debug/boost/intrusive/detail/generic_hook.hpp: At global scope: /opt/boost/trunk-debug/boost/intrusive/detail/generic_hook.hpp:134:55: error: declaration of typedef struct boost::intrusive::hooktags<typename GetNodeAlgorithms::type::node_traits, Tag, LinkMode, BaseHookType> boost::intrusive::generic_hook<GetNodeAlgorithms, Tag, LinkMode, BaseHookType>::hooktags [-fpermissive] /opt/boost/trunk-debug/boost/intrusive/detail/generic_hook.hpp:84:8: error: changes meaning of hooktags from struct boost::intrusive::hooktags<typename GetNodeAlgorithms::type::node_traits, Tag, LinkMode, BaseHookType> [-fpermissive] Ion, could you fix this, please? Regards Hartmut --------------- http://boost-spirit.com http://stellar.cct.lsu.edu

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[move] Documentation example typo.
by Jurko Gospodnetić 04 Aug '13

04 Aug '13

Hi. Just reporting a slight typo in boost::move library documentation's file_descriptor class example code for closing the OS file descriptor. It says: > if(!os_descr_) operating_system_close_file(os_descr_); in its destructor & assignment operator when it should in fact say: > if(os_descr_) operating_system_close_file(os_descr_); [notice the removed ! operator] Hope this helps. Best regards, Jurko Gospodnetić

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[asio] condition_variable for coroutine-powered ASIO
by TONGARI J 04 Aug '13

04 Aug '13

Hi, Since Boost 1.54, ASIO introduced yield_context, which is very helpful to alleviate the pain of writing async ops. Unlike multi-threading, with cooperative multi-tasking, generally we don't have to worry about synchronization, but we still need some sort of mechanism to sync the coroutines in cases like producer-consumer for waiting the data... While I haven't seen any sync tool for asio/coroutine, having a condition_variable or such may be very useful, what do you think? Attached is the poor-man's implementation...

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[utility] [swap] How about Boost.Move?
by Antony Polukhin 03 Aug '13

03 Aug '13

Hi, Sources of Boost.Variant have a swap implementation that takes advantage of move emulation. That code can be useful for Boost.Swap. The idea is not to use std::swap in case of ADL failure, but use a swap implementation that is aware of move emulation: namespace boost_swap_impl { namespace swap_move_emulated { template <typename T> inline void swap(T& lhs, T& rhs) { T tmp( boost::move(lhs) ); lhs = boost::move(rhs); rhs = boost::move(tmp); } } template<class T> void swap_impl(T& left, T& right) { //using namespace std;//use std::swap if argument dependent lookup fails using namespace boost_swap_impl::swap_move_emulated; swap(left,right); } // ... With that code types that use move emulation can be swapped faster and even move only types can be swapped. So, what do the community think about such optimization? -- Best regards, Antony Polukhin

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[git-help] New libraries?
by Rene Rivera 03 Aug '13

03 Aug '13

Today I checked in the new Predef library and I'm wondering, not just for it but in general, if this interim period of svn to git transition what happens to new libraries? Will they automatically show up in the git repos? What are the procedures if the new library is already, originally in git and modularized? 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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[predef] FYI..
by Rene Rivera 01 Aug '13

01 Aug '13

FYI.. to those that care.. I checked in changes to SVN to inject the Predef library into Boost. I say inject because the source is not actually in the SVN repo, it's external and still in github. But is being brought in through their SVN interface. Some testers have already runs the tests for it.. And at some point to be determined with some coordination with the community I will switch the "boost/detail/endian.hpp" header to point to the Predef compatibility equivalent... I suspect at the earliest one more week for that assuming no problems surface. 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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Re: [boost] [multimethods] Proposal: Open Multi-Methods
by Daryle Walker 01 Aug '13

01 Aug '13

//================================================================= From: Jean-Louis Leroy Sent: ‎Saturday‎, ‎July‎ ‎27‎, ‎2013 ‎8‎:‎26‎ ‎PM I am working on library that pretty much implements what Pirkelbauer, Solodkyy and Stroustrup describe in their paper "Open Multi-Methods for C++" - although there are some divergences. I have posted it on GitHub: https://github.com/jll63/multimethods. Please examine the files in the "examples" directory to get an idea of how to use it. [SNIP] The library is essentially feature complete (if anything ever is). I am now going to work on the documentation, a build system, some clean up and compatibility (I tested it only with g++ 4.7.2 only so far). Is there interest in the Boost community for this stuff? If yes, I will adapt it to the guidelines and submit it for formal review. Of course, suggestions are welcome. //================================================================= Are virtual base classes supported? Maybe “virtual_” should be renamed to “virtualize” or “virtualized,” to avoid having a trailing underscore in a non-member name. A good way to document is to write a Doxygen comment as you write your class, function, or macro prototype. It makes you have to think about what the public side of your code has to do. But looking at your “next.cpp” example, you should start with documenting the “selector,” “virtual_,” “MM_CLASS,” “MM_INIT,” “MULTIMETHOD,” “BEGIN_METHOD,” “END_METHOD,” and “initialize” items. Anything in your implementation classes that don’t have to be seen by public code can be make private. Non-public types can go in a detail namespace. Daryle W.

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[boost thread] Catching interrupted exception?
by Philip Bennefall 31 Jul '13

31 Jul '13

Hi all, I have a quick question regarding the interruption of Boost threads. I am making fairly heavy use of the interrupt method call of the thread class, and I am wondering whether I should be catching the boost::thread_interrupted exception from within my thread function? I currently do not and my program runs fine, but I am wondering whether this is defined behavior or whether I should always be catching the exception and returning from the function inside the handler? Kind regards, Philip Bennefall

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Re: [boost] [asio] Randomly having problems reading from the socket
by Marat Abrarov 30 Jul '13

30 Jul '13

> Posted a Bug Report here: Ticket #8937 > <https://svn.boost.org/trac/boost/ticket/8937> Seems like a bug/feature of Windows 7/Vista (or a bug/feature of Windows socket subsystem) - something in background/foreground process scheduling or a memory management issue. Nevertheless it is interesting to know the Asio author's point of view. It will be more clear if the topic starter rewrites his (simple) examples to use WinSock directly rather than through the Asio (use the same time measurement - by means of boost::posix_time). I think that such rewritten examples will show the same behavior. Regards, Marat Abrarov.

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[preprocessor] ARRAY_REPLACE bug?
by Mostafa 30 Jul '13

30 Jul '13

On Windows 7/Cygwin, using boost 1.53, preprocessing the following snippet: pp_array.cc ----------- #include <boost/preprocessor.hpp> //#define BOOST_PP_TUPLE_REM_0() // nothing #define ARRAY (3, (a, x, c)) BOOST_PP_ARRAY_REPLACE(ARRAY, 1, b) via: g++ -E -P -I /... pp_array.cc gives the following incorrect result: (3, (BOOST_PP_TUPLE_REM_0 () a, b , c)) Uncommenting the pound define in the snippet gives the correct result for the preprocessor. Is this a bug?

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[type_erasure] move
by Christophe Henry 29 Jul '13

29 Jul '13

Hi Steven, I'm looking for a crash I get in my own code with g++4.8.1 (4.5 - 4.7 are ok). Maybe you can help me: - there is a copy_constructible concept, but no moveable. Is it enough to add one on the same model? It looks like you std::forward so I'd say yes. Correct? template<class T = _self> struct move_constructible : ::boost::mpl::vector<constructible<T(T&&)>, destructible<T> > {}; - If I std::move a copy_constructible any type by accident, what do I get? A copy? A crash? Thanks, Christophe

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[asio] Randomly having problems reading from the socket
by Torben Wiggerich 29 Jul '13

29 Jul '13

Hi all, I have some problems using the boost.asio.read for a TCP-socket. So far it works fine, but it randomly stops the transfer for at least 5 seconds. To resolve the error I used a simple synchronous server and client from the boost examples and modified it too send a larger amount of data. (307400 Bytes; this size comes from the program I'm trying to get run). On the client side I also changed the reading from the socket to read the complete data with boost.asio.read and transfer_all as argument. Both, server and client, measure the time for sending and reading to the socket and will give an error if it needs more than 1 second. Here is the sourcecode for the server: #include <iostream> #include <string> #include <boost/asio.hpp> #include <boost/date_time/posix_time/posix_time.hpp> using boost::asio::ip::tcp; using namespace boost::posix_time; int main() { try { boost::asio::io_service io_service; tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), 8002)); tcp::socket socket(io_service); acceptor.accept(socket); unsigned char * array = new unsigned char[307400]; for (;;) { boost::system::error_code ignored_error; ptime startTime = microsec_clock::universal_time(); boost::asio::write(socket, boost::asio::buffer( array, 307400 ), boost::asio::transfer_all(), ignored_error); time_duration neededTime = microsec_clock::universal_time() - startTime; if ( neededTime.total_milliseconds() > 1000 ) { std::cout << "ERROR needed too much time: " << neededTime.total_milliseconds() << "ms" << std::endl; } } } catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; } My client sourcecode: #include <iostream> #include <boost/array.hpp> #include <boost/asio.hpp> #include <boost/date_time/posix_time/posix_time.hpp> using boost::asio::ip::tcp; using namespace boost::posix_time; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: client <host>" << std::endl; return 1; } boost::asio::io_service io_service; boost::asio::ip::tcp::endpoint endpoint( boost::asio::ip::address::from_string( argv[1] ), 8002 ); tcp::socket socket(io_service); boost::system::error_code error = boost::asio::error::host_not_found; socket.connect( endpoint, error ); if (error) throw boost::system::system_error(error); int counter = 0; unsigned char* array = new unsigned char[307400]; for (;;) { boost::system::error_code error; ptime startTime = microsec_clock::universal_time(); size_t len = boost::asio::read( socket, boost::asio::buffer( array, 307400 ), boost::asio::transfer_all(), error ); time_duration neededTime = microsec_clock::universal_time() - startTime; if ( error ) { printf( "body read error %s\n", error.message().c_str() ); } if ( counter % 5000 == 0 ) { std::cout << "passed: " << counter << "\r"; } ++counter; if ( neededTime.total_milliseconds() > 1000 ) { std::cout << "ERROR needed too much time: " << neededTime.total_milliseconds() << "ms" << std::endl; } } } catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; } To reproduce the error just let it run for a while. It can take up to 30 minutes or even more... After a while it will produce the line: "ERROR needed too much time: 5007ms". Maybe with slightly different times, but all around 5 seconds. I tested it on different machines with Windows Vista and Seven. So am I'm doing sth. wrong? Is the reading from the socket correct? I'm using boost version 1.44. Kind regards Torben Wiggerich

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New failing tests in circular buffer on some platforms
by Paul A. Bristow 29 Jul '13

29 Jul '13

I note that there are some new failing tests for circular buffer on some platforms http://www.boost.org/development/tests/trunk/developer/circular_buffer.html on MSVC noncopyable_movable_noexcept_t is causing trouble base_test.cpp C:\boost_regression\trunk\boost\boost/circular_buffer/base.hpp(694) : error C2558: struct 'noncopyable_movable_noexcept_t' : no copy constructor available or copy constructor is declared 'explicit' C:\boost_regression\trunk\boost\boost/circular_buffer/base.hpp(673) : while compiling class template member function 'noncopyable_movable_noexcept_t *boost::circular_buffer<T>::linearize(void)' with [ T=noncopyable_movable_test_t ] c:\boost_regression\trunk\boost\libs\circular_buffer\test\common.ipp(2160) : see reference to function template instantiation 'noncopyable_movable_noexcept_t *boost::circular_buffer<T>::linearize(void)' being compiled with [ T=noncopyable_movable_test_t ] c:\boost_regression\trunk\boost\libs\circular_buffer\test\common.ipp(2236) : see reference to class template instantiation 'boost::circular_buffer<T>' being compiled with [ T=noncopyable_movable_test_t ] C:\boost_regression\trunk\boost\boost/circular_buffer/base.hpp(697) : error C2558: struct 'noncopyable_movable_noexcept_t' : no copy constructor available or copy constructor is declared 'explicit' ON gcc and Clang there are warnings and failure Running 60 test cases... ../libs/circular_buffer/test/common.ipp(2303): error: in "check_containers_exception_specifications": check boost::has_nothrow_constructor<circular_buffer<int> >::value has failed Can any experts shed light on this? I do not believe that the underlying circular buffer code has changed recently. Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow(a)hetp.u-net.com

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[thread] Questions about broken_promise
by Klaim - Joël Lamotte 29 Jul '13

29 Jul '13

I have a few questions concerning broken promises (exception): 1. is the broken_promise exception a standard, or future standard behaviour? So far I assumed it wasn't because http://en.cppreference.com/w/cpp/thread/promise/~promise don't say anything about this and I only read about broken_promise exceptions on Boost.Thread documentation. I would like to know if I should expect the future standard library to have the same concept. I see no configuration macro to deactivate these exceptions. I don't want to actually, but if I'm correct that it's not standard or future standard, then it's surprising that I can't setup a standard-like setup. 2. I have a case that could be summarized like this: ///////////////////////////////////////////// Updated by thread A: struct X { /*... */ }; struct K { future<shared_ptr<X,U>> m_ft_x; shared_ptr<X,U> m_x; K( Foo& foo ) : m_ft_x( foo.create<X>() ) {} void update() // this is always called by a loop in the thread A { if( !m_x ) { if( m_ft_x.has_value() ) m_x = m_ft_x.get(); } else work(); } void work(); // uses m_x }; Updated by thread B: // special deleter which will just push a task in Foo work queue for deleting the object // in sync with thread B struct U { /* ... */ }; struct Foo { template< class T > future<shared_ptr<T,U>> create() // will push a creation task in a work queue updated in update() void update(); // called by a loop in the thread B, will execute all the work pushed in the work queue. }; ///////////////////////////////////////////// (this is an exageratedly simplified version of what I'm doing) It works nicely (even if I think it could be improved with future.then and other tools) but there is a minor problem appearing when an instance of K is constructed then almost immediately destructed, before the instance of Foo executed the creation of the X instance. In this case, visual studio (which is configured to detect all throw calls) detect a broken_promise exception thrown from the destructor of the promise which was in the code generated by Foo::create() and pushed in a work queue. I look at the destructor and I see: if(!future_->done && !future_->is_constructed) { future_->mark_exceptional_finish_internal(boost::copy_exception(broken_promise()), lock); } Here is the full copy_exception code: template <class T> inline exception_ptr copy_exception( T const & e ) { try { throw enable_current_exception(e); } catch( ... ) { return current_exception(); } } This code triggers actually two "first-chance" exceptions this is the first one) which are catch immediately intentionally. My question is: why is copy_exception necessary and why does it have to do it this way? It's a very minor problem as just re-setting my visual studio debugging settings to default makes the exception transparent -only visible in the console log. However each time I activate debug breaking on all c++ exception so that I can debug some potential issues, I can have a breakpoint which is actually "noise" as it is only used to implement a copy of exception. Is it possible to eliminate this noise? Or, as I'm guessing, is there a language or compiler limitation which forces this code to be written this way? Thanks for your time. Joel Lamotte

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safe bool not safe enough ?
by John Maddock 28 Jul '13

28 Jul '13

Just discovered (oops!) that the so called safe bool ideom is not as safe as it appears, for example: class Testable { bool ok_; typedef void (Testable::*bool_type)() const; void this_type_does_not_support_comparisons() const {} public: explicit Testable(bool b=true):ok_(b) {} operator bool_type() const { return ok_==true ? &Testable::this_type_does_not_support_comparisons : 0; } }; Testable t(true); bool b = t; // Compiles OK - Ooops! Which is causing multiprecision to misbehave when used in conjunction with uBlas: https://svn.boost.org/trac/boost/ticket/8292#comment:2 I guess making the conversion explicit in C++11 mode would help (I still need to test that), but is there a C++03 solution? Thanks, John.

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radix sort
by Sourav 28 Jul '13

28 Jul '13

Hi All, I wanted to know if someone is/was working on Radix Sort or not. I did check the SoC listings and did not see radix sort in the list. If no one is working, may someone help me provide some pointers/details as to what the expectation is with regards to Radix sort for boost ? Regards, -Sourav

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boost::python help?
by David M. Cotter 26 Jul '13

26 Jul '13

i'd like my app to be "available" to python while it's running. for example, say my app is "FooBar.app". when my FooBar.app is running, now there is a python interface available to python, and the user can write python scripts to make use of it with their scripts, they can control my running application when FooBar.app is NOT running, perhaps making use of any of the python functions of "FooBar.app" would either return an error, or possibly launch "FooBar.app". can boost::python help with this? i've never worked with extending or embedding python, so any help would be super great

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Patch bonanza for VS2013 Preview support
by Lars Viklund 25 Jul '13

25 Jul '13

Hi list. What's the best way to spend your vacation if not trying to get Boost to build on bleeding-edge compilers. I set out to see how well Boost 1.54.0 behaved on the newly released go-live-ready Visual Studio 2013 Preview. Below is the list of bugs filed against Boost and Microsoft. Enjoy. With these patches in place, I can get a complete build working with all libraries normally available on a fresh machine (means that I didn't test Python, MPI, ICU, compressed streams). I haven't been able to find out how to run the tests in any human-readable form, but this should not cause any regressions as it's either increasing workaround bounds or adding headers that the standard mandates already. Boost.Config VS2013 Preview version bump https://svn.boost.org/trac/boost/ticket/8753 The Visual Studio 2013 Preview toolchain has _MSC_VER 1800 and _MSC_FULL_VER 180020617. See the attached patch for the minimum changes that are needed to get anywhere at all. Boost.Build needs support for the VS2013 Preview toolset (18.00.20617.1) https://svn.boost.org/trac/boost/ticket/8754 Visual Studio 2013 Preview is out and claims to be 12.0. I copy-pasted everything related to 11.0 to refer to 12.0 and it Works On My Machine, see attached patch. Boost.Signals VS2013 Preview version bump https://svn.boost.org/trac/boost/ticket/8755 The BOOST_WORKAROUND macros at boost/signals/detail/named_slot_map.hpp:130 and libs/signals/src/named_slot_map.cpp:27 needs to be increased to <= 1800 in order to encompass the Visual Studio 2013 Preview compiler. Boost.MPL VS2013 Preview version bump https://svn.boost.org/trac/boost/ticket/8756 The BOOST_WORKAROUND macros at boost/mpl/assert.hpp lines 37 and 247 need to be changed to also consider BOOST_MSVC, == 1800, patch attached. Boost.Serialization lacks algorithm header include for std::min https://svn.boost.org/trac/boost/ticket/8757 The <algorithm> header providing std::min is not included in boost/archive/iterators/transform_width.hpp, this breaks on Visual Studio 2013 Preview due to library changes. Boost.Asio lacks algorithm header include for std::min https://svn.boost.org/trac/boost/ticket/8758 The <algorithm> header providing std::min is not included in boost/asio/detail/impl/win_iocp_io_service.hpp, this breaks on Visual Studio 2013 Preview due to library changes. std::bind broken with boost/tuple/tuple.hpp or anything else providing a ADL tie https://connect.microsoft.com/VisualStudio/feedback/details/792163/std-bind… Not our fault, I filed a bug on Connect and am hoping that they'll notice it before RTM. 'std::bind' finds our 'tie' if a type from a boost namespace is used in the 'std::function' argument type list. -- Lars Viklund | zao(a)acc.umu.se

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