- Boost - lists.boost.org

Move semantics for std::string?
by Robert Dailey 17 Feb '12

17 Feb '12

I'm using C++03 and would love some way to apply move semantics to a std::string. Can boost facilitate this in some way without using smart pointers? Consider an example like below (This is a contrived example, so assume NRVO does not apply): std::string GetInformation( int someNumber ) { // We use 'someNumber' to look up a string std::string myValue( "hello world" ); // Create the string here return myValue; } Above, the return value would result in a copy, I'd like to move it instead. --------- Robert Dailey

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RFC: runtime-flexible arrays
by Bjoern Andres 17 Feb '12

17 Feb '12

Hi everyone, I have written a header for runtime-flexible multi-dimensional views and arrays and would love to get comments and feedback from the boost community: tutorial code : http://tinyurl.com/7hdldc9 main website : http://www.andres.sc/marray.html doxygen reference doc: http://www.andres.sc/marray/doc/index.html git repository : https://github.com/bjoern-andres/marray tech report : http://arxiv.org/pdf/1008.2909v1 Unlike in Boost.MultiArray, the dimension of arrays is not a template parameter in Marray. Other features include - runtime-flexible dimension, shape, size and indexing order (first or last coordinate major order) - arithmetic operators with automatic type promotion and expression templates. - access to entries via coordinates, scalar indices and STL-compliant random access iterators. - derived classes for matrices and vectors - support of exchangeable STL-compliant allocators. Thanks for your consideration Bjoern

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boost thread rev 77005 fails on cygwin due SIGSTKSZ not defined
by Bernd Prager 17 Feb '12

17 Feb '12

All, Boost Thread no longer compiles on Cygwin 1.7.10 / g++ (GCC) 4.5.3 since SIGSTKSZ is not defined on this platform: cc.compile.c++ bin.v2/libs/context/build/gcc-4.5.3/release/threading-multi/stack_utils_posix.o libs\context\src\stack_utils_posix.cpp: In function ‘rlimit<unnamed>::stacksize_limit_()’: libs\context\src\stack_utils_posix.cpp:27:15: warning: unused variable ‘result’ libs\context\src\stack_utils_posix.cpp: In function ‘size_t boost::contexts::minimum_stacksize()’: libs\context\src\stack_utils_posix.cpp:52:10: error: ‘SIGSTKSZ’ was not declared in this scope libs\context\src\stack_utils_posix.cpp:52:20: warning: control reaches end of non-void function Any suggested workarounds? Thank you, -- Bernd

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Can't build boost 1.48 with STLport 5.2.1
by Robert Dailey 17 Feb '12

17 Feb '12

I'm trying to get Boost 1.48 building using STLport 5.2.1. I am on Windows 7 x64. Here is what I've done: 1. Update tools/build/v2/user-config.jam with the following: using msvc : 7.1 ; using stlport : 5.2.1 : C:/Code/third_party_source/STLport-5.2.1/stlport : C:/Code/third_party_source/STLport-5.2.1/lib ; 2. Run the following command through the VS2003 command line tool: bootstrap.bat 3. This sets up the b2 executable and stuff, after that I run: b2 toolset=msvc link=shared threading=multi runtime-link=shared variant=debug stdlib=stlport --layout=tagged stage However, once it comes time to link the first library (boost filesystem), I get a ton of linker errors, mostly LNK2001 relating to unresolved STLport symbols. Here is one of the first ones: path.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public: __thiscall stlpd _std::basic_string<wchar_t,class stlpd_std::char_traits<wchar_t>,class stlpd_std::allocator<wchar_t> >::basic_string<wchar_t,class stlpd_std::char_traits<wchar_t>,class stlpd_std::allocator<wchar_t> > (class stlpd_std::basic_string<wchar_t,class stlpd_std::char_traits<wchar_t>,class stlpd_std::alloca tor<wchar_t> > const &)" (__imp_??0?$basic_string@_WV?$char_traits@ _W@stlpd_std@@V?$allocator@_W@2@@ stlpd_std@@QAE@ABV01@@Z) Anyone have any idea how I can get this working? --------- Robert Dailey

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Boost.Asio documentation needs to be updated
by Bernd Prager 17 Feb '12

17 Feb '12

All, The documentation states that Boost.Asio requires __USE_W32_SOCKETS must be defined when using Cygwin. That doesn't seem to be true any longer. When I define __USE_W32_SOCKETS compilation of several components (e.g. ./boost/test/impl/debug.ipp) fail with "error: '::select' has not been declared". Without that definition compilation works apparently fine. Regards, -- Bernd

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[Block Pointer] Questions?
by Phil Bouchard 17 Feb '12

17 Feb '12

Hi, I was wondering if anybody had any question regarding Block Pointer. It might be hard to convince Java and C# authors garbage collectors are nonsense but we do not have that burden here. Thank you, -Phil Author of "Finite Theory of the Universe, Dark Matter Disproof and Faster-Than-Light Speed": http://bookstore.authorhouse.com/Products/SKU-000539350/Finite-Theory-of-th…

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[exception] warning about non-virtual destructor - resolution?
by Nathan Ridge 16 Feb '12

16 Feb '12

Hello, GCC 4.7 introduces a new warning [1] that warns about calling "delete" on a pointer of a type that has virtual functions but a nonvirtual destructor. This warning is enabled with -Wall. As a result, even something as trivial as the following: #include <boost/thread/future.hpp> when compiled with -Wall, produces a warning like this: In file included from boost/boost/smart_ptr/shared_ptr.hpp:30:0, from boost/boost/shared_ptr.hpp:17, from boost/boost/date_time/time_clock.hpp:17, from boost/boost/thread/thread_time.hpp:9, from boost/boost/thread/future.hpp:13, from Source/timetable.cpp:1: boost/boost/checked_delete.hpp: In instantiation of 'void boost::checked_delete(T*) [with T = boost::error_info<boost::tag_original_exception_type, const std::type_info*>]': boost/boost/smart_ptr/detail/shared_count.hpp:95:13: required from 'boost::detail::shared_count::shared_count(Y*) [with Y = boost::error_info<boost::tag_original_exception_type, const std::type_info*>]' boost/boost/smart_ptr/shared_ptr.hpp:177:50: required from 'boost::shared_ptr<T>::shared_ptr(Y*) [with Y = boost::error_info<boost::tag_original_exception_type, const std::type_info*>; T = boost::error_info<boost::tag_original_exception_type, const std::type_info*>]' boost/boost/exception/info.hpp:171:69: required from 'const E& boost::exception_detail::set_info(const E&, const boost::error_info<Tag, T>&) [with E = boost::unknown_exception; Tag = boost::tag_original_exception_type; T = const std::type_info*]' boost/boost/exception/info.hpp:192:46: required from 'typename boost::enable_if<boost::exception_detail::derives_boost_exception<E>, const E&>::type boost::operator<<(const E&, const boost::error_info<Tag, T>&) [with E = boost::unknown_exception; Tag = boost::tag_original_exception_type; T = const std::type_info*; typename boost::enable_if<boost::exception_detail::derives_boost_exception<E>, const E&>::type = const boost::unknown_exception&]' boost/boost/exception/detail/exception_ptr.hpp:182:13: required from 'void boost::unknown_exception::add_original_type(const E&) [with E = std::exception]' boost/boost/exception/detail/exception_ptr.hpp:161:32: required from here boost/boost/checked_delete.hpp:34:5: warning: deleting object of polymorphic class type 'boost::error_info<boost::tag_original_exception_type, const std::type_info*>' which has non-virtual destructor might cause undefined behaviour [-Wdelete-non-virtual-dtor] Note that the same code compiled without warnings with GCC 4.6. I've read this thread [2] about this issue, but it's not clear what the agreed-upon resolution was. In light of this new warning, can the code be revised to avoid it? Or is it the position of the library maintainers that GCC is in error to give a warning in this case, in which case I should file a GCC bug? Or is there some other recommended resolution? Thanks, Nate [1] http://gcc.gnu.org/gcc-4.7/changes.html#cxx [2] http://boost.2283326.n4.nabble.com/boost-exception-detail-error-info-base-d…

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fix links in boost.container docs
by niXman 16 Feb '12

16 Feb '12

Hello list! Diff file is attached. niXman.

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Re: [boost] [optional] generates unnessesary code for trivial types
by Andrzej Krzemienski 16 Feb '12

16 Feb '12

> > FYI I'm currently working closely with Andrzej Krzemienski on a std proposal which, among other things, involves the long awaited update to the Boost implementation. > > Could you give a use case for optional<T&>. When reading the doc about I completely understand the other use cases: > * return types > * parameters > * locals > * members > * expensive unnecessary default construction > We could be having the same conversation about optional<bool>. Here the documentation is clear: it works as expected but is the user probably should be using tri-state. > We could optimize optional<bool> to store ~0 to indicate unset. I personally don't think it's worth doing that, since use case is questionable. > As far as I can tell optional<T&> is a type which can be easily confused with optional<T>, but is really equivalent to T*. It also allows for debates about the meaning of reassignment. > I'm not dead set against this optimization. I'm just wondering if anyone will really benefit and if it's worth adding a specialization + tests. Speaking for myself, I do not have a need for optional reference. I have been using Boost.Optional for many years, I find it extremely useful; and I never had a use case for optional reference. On the other hand, others seem to be in need of optional references.Andrey said in this thread that that he wants to use it. The only two motivating use cases that triggered the addition of optional references (that I am aware of) is the interface of Boost.Variant (see http://lists.boost.org/Archives/boost/2003/02/44585.php) and the use case for Boost.Spirit (see http://lists.boost.org/Archives/boost/2003/10/55584.php) I would be reluctant to just discard these use cases. On the other hand, if they are allowed, the controversy of assignment arises. One thing to note is the requirement for optional references is not motivated by optimization opportunities, but additional behavior. > Side question: is streamablity going to be in your proposal? It is not currently. The reason for that is that there is no clear way how it should be implemented (a similar issue applies to pairs, tuples, variant, any, etc...) See http://lists.boost.org/Archives/boost/2005/03/81619.php for discussion. I believe that the problem is with the streaming itself. For instance, should streaming out and then streaming the result back in produce the same value? Some people expect that, but even std::string could not provide this behavior. Regards, &rzej

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Boost Graph Library - serialization of subgraph
by Ernest Galbrun 16 Feb '12

16 Feb '12

Dear fellow boost member, I am currently using the boost graph library, and especially the subgraph features. As there is no serialization feature for subgraphes, I have developped my own, by modifying the one developed by Rakuto that was broken, probably due to some changes in the graph library ( http://rakuto.blogspot.com/2008/12/c-library-for-serialazation-of.html ). If you think it would be useful, I could do the remaining work (that is thorough testing and debugging, and providing automated test case, maybe I am forgetting something ?). The bottom line is that I am new to this kind of project, and I will probably need some kind of guidance about the way to contribute. sincerely yours, -- Ernest Galbrun

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