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[Boost.Python] Making Python classes and functions available to C++
by Sean Farrow 13 Jul '21

13 Jul '21

Hi all, What is the easiest way of making Python classes and functions available to external C++ applications. The Boost.Python documentation seems to show making C++ classes available to Python, but I can't find anything that shows going the other way. Any help appreciated. Kind regards Sean.

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assembler error while using boost_geometry on HPUX IA64
by Ananta Swain 13 Jul '21

13 Jul '21

Hi Boost Experts, I am using boost geometry headers in our code. While compiling the code on HPUX IA64 with +std=c++11 and +stl=gnu flags, we get a cryptic assembler error. Appreciate any help to understand/debug this error. The testcase: *bash-4.3$ cat geom1.cpp* #include <boost/geometry.hpp> #include <boost/geometry/geometries/linestring.hpp> #include <boost/geometry/geometries/point_xy.hpp> #include <boost/geometry/geometries/multi_linestring.hpp> typedef boost::geometry::model::point<double, 2, boost::geometry::cs::geographic<boost::geometry::degree> > point_t; typedef boost::geometry::model::linestring<point_t > linestring_t; typedef boost::geometry::model::multi_linestring<linestring_t > multilinestring_t; using namespace std; template<typename T, typename S> bool Inside(string one, string two) { T objOne; S objTwo; bool inside = false; boost::geometry::read_wkt(one, objOne); boost::geometry::read_wkt(two, objTwo); inside = boost::geometry::within(objOne, objTwo); return inside; } bool Inside(string wktOne, string wktTwo) { bool inside; inside = Inside<multilinestring_t, linestring_t>(wktOne, wktTwo); return inside; } Compilation command: *bash-4.3$ aCC -c +DD64 +std=c++11 +stl=gnu -I <boost_headers path> geom1.cpp* *ASM_BACKEND fatal error: symbol* `_ZN5boost8geometry6detail7overlay27get_turn_info_linear_linearINS1_6relate5turns13assign_policyILb1EEEE22append_opposite_spikesILNS3_INS6_ILb1EEEE14append_versionE1ENS2_9turn_infoINS0_5model5pointIdLm2ENS0_2cs10geographicINS0_6degreeEEEEENS0_13segment_ratioIdEENS2_21turn_operation_linearINSB_IdLm2ENSD_ISE_EEEENSF_IdEEEENS_5arrayINSG_INSB_IdLm2ENSD_ISE_EEEENSF_IdEEEELm2EEEEENS2_17intersection_infoINS1_9get_turns29unique_sub_range_from_sectionILb0ENS0_7sectionINSA_3boxINSB_IdLm2ENSD_ISE_EEEEEELm2EEENSB_IdLm2ENSD_ISE_EEEENS0_22ever_circling_iteratorIN9__gnu_cxx17__normal_iteratorIPKNSB_IdLm2ENSD_ISE_EEEESt6vectorINSB_IdLm2ENSD_ISE_EEEESaINSB_IdLm2ENSD_ISE_EEEEEEEEEENS0_8strategy12intersection18spherical_segmentsIvEENS1_17no_rescale_policyEEENSK_ILb0ENSL_INSM_INSB_IdLm2ENSD_ISE_EEEEEELm2EEENSB_IdLm2ENSD_ISE_EEEENSN_INSP_ISR_SS_INSB_IdLm2ENSD_ISE_EEEESaINSB_IdLm2ENSD_ISE_EEEEEEEEEENSV_IvEESW_EENSB_IdLm2ENSD_ISE_EEEENSV_IvEESW_EESt20back_insert_iteratorISS_INS9_INSB_IdLm2ENSD_ISE_EEEENSF_IdEENSG_INSB_IdLm2ENSD_ISE_EEEENSF_IdEEEENSH_INSG_INSB_IdLm2ENSD_ISE_EEEENSF_IdEEEELm2EEEEESaINS9_INSB_IdLm2ENSD_ISE_EEEENSF_IdEENSG_INSB_IdLm2ENSD_ISE_EEEENSF_IdEEEENSH_INSG_INSB_IdLm2ENSD_ISE_EEEENSF_IdEEEELm2EEEEEEEEEEbRT0_RKT1_T2_' already defined Thanks, Ananta

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interprocess, how to grow managed_mapped_file when it used to store map<>
by i.nixman＠autistici.org 12 Jul '21

12 Jul '21

hi guys! I want to use boost::interprocess to store some resources (strings) into `bi::map<bi::string, bi::string>` that uses `bi::managed_mapped_file` so I can put the resources in the map once, take the file, and distribute it with the program. the problem is that I cannot calculate the required size in advance, so I want to use `bi::managed_mapped_file::grow ()` before inserting another element into the map. but it doesn't work as i expected, at some point i get exception: what(): boost::interprocess::bad_alloc I know the length of the key string and the length of the value string, how can I find out the size by which I must `grow()` before inserting another element into the map? now my code looks like this: #include <boost/interprocess/managed_mapped_file.hpp> #include <boost/interprocess/allocators/allocator.hpp> #include <boost/interprocess/containers/map.hpp> #include <boost/interprocess/containers/string.hpp> #include <iostream> int main () { namespace bi = boost::interprocess; using segment_manager_t = bi::managed_mapped_file::segment_manager; using void_allocator = bi::allocator<void, segment_manager_t>; using char_allocator = bi::allocator<char, segment_manager_t>; using char_string = bi::basic_string<char, std::char_traits<char>, char_allocator>; using map_value_type = std::pair<const char_string, char_string>; using map_value_type_allocator = bi::allocator<map_value_type, segment_manager_t>; using map_type = bi::map<char_string, char_string, std::less<char_string>, map_value_type_allocator>; static const char *mapfname = "map.dat"; bi::managed_mapped_file mmfile(bi::open_or_create, mapfname, 1024); { void_allocator alloc_inst(mmfile.get_segment_manager()); map_type *mymap = mmfile.find_or_construct<map_type>("MyMap")(alloc_inst); assert(mymap); for ( int i = 0; i < 100; ++i ) { std::string s = std::to_string(i); char_string key(s.c_str(), alloc_inst); char_string value(s.c_str(), alloc_inst); // bi::managed_mapped_file::grow(mapfname, ???); <<<<<<<<<<<<<<<<<<<<<< mymap->emplace(std::move(key), std::move(value)); } } bi::managed_mapped_file::shrink_to_fit(mapfname); return 0; } (or: https://wandbox.org/permlink/jtTOzlMh16ZS8jG6) any ideas? best!

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[release] Boost 1.77.0 Beta 1 Release Candidate 1 is available
by Marshall Clow 10 Jul '21

10 Jul '21

The first release candidates for the 1.77.0 beta release are now available at: https://boostorg.jfrog.io/artifactory/main/beta/1.77.0.beta1/source/ 1aba2bf9416d71026c9e6bbd10a2b7cfb31b0950baa7ad0861dfb74984d96bd9 boost_1_77_0_b1_rc1.zip 55126d149664541ffc9fd1f41b2ec67146d69bdab92e41da4bb8610b755ca9ec boost_1_77_0_b1_rc1.7z 1aabe7704e91f4f8d97b81d03ddc21c3396f4b72fc4041f01bfcfc128bac0d73 boost_1_77_0_b1_rc1.tar.gz 3d5801790c96d2bc9ed23372c4f9fd963bc2f39fe540e35d7b4fe586ba77dfa7 boost_1_77_0_b1_rc1.tar.bz2 The web site has NOT YET been updated. As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Release managers

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Boost on apple silicon
by simsicon 06 Jul '21

06 Jul '21

Hi, I was following the tutorial ( https://www.boost.org/doc/libs/1_76_0/doc/html/boost_asio/tutorial/tuttimer…) on macbook with m1 chip, and try to run the simple code and I meet the following error: Undefined symbols for architecture arm64: "boost::chrono::steady_clock::now()", referenced from: boost::asio::detail::chrono_time_traits<boost::chrono::steady_clock, boost::asio::wait_traits<boost::chrono::steady_clock> >::now() in mock-93ab24.o ld: symbol(s) not found for architecture arm64 clang: error: linker command failed with exit code 1 (use -v to see invocation) I am kind of new to C++ and boost, but I think this issue may be related to apple silicon compatibility? -- Thanks&Best Regards Zhang Zheng

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boost iterator range and filter iterator exception using MSVC
by Olaf Peter 02 Jul '21

02 Jul '21

Hi, using MSVC 2019 in debug mode I get an exception "cannot compare incompatible string_view iterators for equality". Using release mode and Clang/G++ all went fine as expected. - Boost: 1.76 - Visual Studio 2019 16.10.3 in C++17 mode How can it changed to be "portable" for all compiler? What's the reason behind? Using range.data() + size or data.front() + size for e.g. end iterator didn't compile. Thanks in advance! Olaf #include <boost/iterator/filter_iterator.hpp> #include <boost/range/iterator_range.hpp> #include <boost/range/iterator_range_core.hpp> #include <boost/range/iterator_range_io.hpp> #include <string_view> #include <iostream> template <typename RangeType> static auto filter_range(RangeType const& range) { struct separator_predicate { bool operator()(char x) { return '_' != x; } }; // FixMe: MSVC 2019 with '_CONTAINER_DEBUG_LEVEL > 0' triggers // assertion: // "cannot compare incompatible string_view iterators for equality" return boost::make_iterator_range( boost::make_filter_iterator( separator_predicate{}, range.begin(), range.end()), boost::make_filter_iterator( separator_predicate{}, range.end())); } using iterator_type = std::basic_string_view<char>::const_iterator; using string_span = boost::iterator_range<iterator_type>; int main() { // input std::string_view const sv = "Hello_World"; // algorithm get boost::iterator_range, aka string_span auto const range = string_span(sv); // here we are auto const range_f = filter_range(range); std::cout << range_f << '\n'; }

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[nowide] Convert wstring to u8string (C++20)
by Jim Orcheson 01 Jul '21

01 Jul '21

In C++17 and earlier, nowide::narrow can be used to convert from UTF-16 encoded strings (std::wstring) to UTF-8 encoded strings, stored in std::string. C++20 introduced std::u8string for UTF-8 encoded strings and it is incompatible with std::string. Is there some way I can get from std::wstring to std::u8string? It is not at all obvious from the nowide documentation.

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[MP11] Initialize the Nth alternative of an std::variant based on a runtime index
by Dominique Devienne 01 Jul '21

01 Jul '21

Hi. I'm modernizing some code, to use std::variant instead of ad-hoc peudo-variant structs. These structs need to be encoded/decoded via avro::codec_traits specializations, but given that std::variant is variadic, I'm struggling a bit. I've done my research and found peter's [1] and also looked at [2], which I thought might work, but does not, and I don't understand the errors I'm getting with MSVC 2019 in C++17 mode. The code is below, with also a subset of the compiler errors I'm getting. [1] https://www.reddit.com/r/cpp/comments/f8cbzs/creating_stdvariant_based_on_i… [2] https://www.boost.org/doc/libs/develop/libs/mp11/doc/html/mp11.html#mp_with… template <> struct codec_traits<std::monostate> { static void encode(Encoder& e, const std::monostate&) { e.encodeNull(); } static void decode(Decoder& d, std::monostate&) { d.decodeNull(); } }; template <typename... Ts> struct codec_traits<std::variant<Ts...>> { static void encode(Encoder& e, const std::variant<Ts...>& var) { e.encodeUnionIndex(var.index()); std::visit( [&e](const auto& alternative) { avro::encode(e, alternative); }, var ); } static void decode(Decoder& d, std::variant<Ts...>& var) { const size_t index = d.decodeUnionIndex(); if (index >= sizeof...(Ts)) { throw avro::Exception("Invalid Union index"); } auto& alternative = boost::mp11::mp_with_index<sizeof...(Ts)>( index, [&var](auto I) { return var.emplace<I>(); // I is mp_size_t<index>{} here } ) ; avro::decode(d, alternative); } }; 1>Messages.cpp 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\Messages.hpp(70,1): error C2220: the following warning is treated as an error 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\Messages.hpp(70,1): warning C4239: nonstandard extension used: 'initializing': conversion from 'std::monostate' to 'std::monostate &' 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\Messages.hpp(70,1): message : A non-const reference may only be bound to an lvalue 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\Messages.hpp(70): message : while compiling class template member function 'void avro::codec_traits<T>::decode(avro::Decoder &,std::variant<std::monostate,int64_t,double> &)' 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v 1> ] 1>D:\pdgm\kits\trunk\Avrocpp\1.9.2-Boost-1.74.0\Win_x64_10_v16_debug\include\avro/Specific.hh(341): message : see reference to function template instantiation 'void avro::codec_traits<T>::decode(avro::Decoder &,std::variant<std::monostate,int64_t,double> &)' being compiled 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v 1> ] 1>D:\pdgm\kits\trunk\Avrocpp\1.9.2-Boost-1.74.0\Win_x64_10_v16_debug\include\avro/Specific.hh(333): message : see reference to class template instantiation 'avro::codec_traits<T>' being compiled 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v 1> ] 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\codegen/Messages.i.ipp(1527): message : see reference to function template instantiation 'void avro::encode<pdgm::eml::etp12::Datatypes::IndexValue_item_v>(avro::Encoder &,const T &)' being compiled 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v 1> ] 1>D:\pdgm\kits\trunk\boost\1.74.0\Win_x64_10_v16_debug\include\boost/mp11/detail/mp_with_index.hpp(87,1): error C2440: 'return': cannot convert from '__int64' to 'std::monostate' 1>D:\pdgm\kits\trunk\boost\1.74.0\Win_x64_10_v16_debug\include\boost/mp11/detail/mp_with_index.hpp(87,1): message : No constructor could take the source type, or constructor overload resolution was ambiguous 1>D:\pdgm\kits\trunk\boost\1.74.0\Win_x64_10_v16_debug\include\boost/mp11/detail/mp_with_index.hpp(371): message : see reference to function template instantiation 'std::monostate boost::mp11::detail::mp_with_index_impl_<3>::call<0,_Ty>(size_t,F &&)' being compiled 1> with 1> [ 1> _Ty=avro::codec_traits<pdgm::eml::etp12::Datatypes::IndexValue_item_v>::decode::<lambda_7e593df011d98e42859c6ecb357b3e3f>, 1> F=avro::codec_traits<pdgm::eml::etp12::Datatypes::IndexValue_item_v>::decode::<lambda_7e593df011d98e42859c6ecb357b3e3f> 1> ] 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\Messages.hpp(70): message : see reference to function template instantiation 'std::monostate boost::mp11::mp_with_index<3,avro::codec_traits<T>::decode::<lambda_7e593df011d98e42859c6ecb357b3e3f>>(size_t,F &&)' being compiled 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v, 1> F=avro::codec_traits<pdgm::eml::etp12::Datatypes::IndexValue_item_v>::decode::<lambda_7e593df011d98e42859c6ecb357b3e3f> 1> ] 1>D:\pdgm\trunk\psc3\SharedComponents\src\lib\pdgm\eml\etp12\Messages.hpp(70): message : while compiling class template member function 'void avro::codec_traits<T>::decode(avro::Decoder &,std::variant<std::monostate,int64_t,double> &)' 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v 1> ] 1>D:\pdgm\kits\trunk\Avrocpp\1.9.2-Boost-1.74.0\Win_x64_10_v16_debug\include\avro/Specific.hh(341): message : see reference to function template instantiation 'void avro::codec_traits<T>::decode(avro::Decoder &,std::variant<std::monostate,int64_t,double> &)' being compiled 1> with 1> [ 1> T=pdgm::eml::etp12::Datatypes::IndexValue_item_v 1> ]

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[Asio] boost::system symbols visible despite BOOST_ASIO_DISABLE_VISIBILITY being defined
by Angela Breuer 30 Jun '21

30 Jun '21

Hello, I'm developing a C++11 shared library that uses Boost.Asio (with Boost version 1.72) as a header-only library. Exceptions are disabled as the library is intended to be used on embedded devices that do not support exceptions and, to ensure this is the case, all interfaces in my library have the noexcept operator and I have BOOST_EXCEPTION_DISABLE and BOOST_NO_EXCEPTIONS defined. Additionally, all public interfaces in the library do not expose any Boost / Boost.Asio types. When attempting to hide private symbols in my shared library with the GCC visibility flags and annotations (i.e. -fvisibility=hidden), I learned that I needed to define BOOST_ASIO_DISABLE_VISIBILITY to disable the visibility pragmas in Boost.Asio so the boost::asio symbols will also be hidden. Although I was able to hide the boost::asio symbols with this strategy, this still results in a subset of boost::system symbols being visible. I do have some internal helper free functions that accept a boost::system::error_code. I suspect that they may have something to do with these visible symbols, but they are completely internal to the library and the symbols for those helper functions are not visible when I inspect the library's symbols with nm -DC. I will note that I was able to hide the boost::system symbols by using a linker version script, but I do not wish to maintain an unwieldy list of symbols to export if I can help it. Is there a supported way to hide the boost::system symbols aside from using a linker version script? I have attached nm -DC output along with gcc / g++ invocations for reference. Thank you, -Angela

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MSVC compiler error with boost ver 1.71
by John Emmas 24 Jun '21

24 Jun '21

Hi there - I'm using boost ver 1.71 and I'm seeing a strange problem with VS2019. Simply #including this line at the top of a source file will generate a compiler error if I try to build in Debug mode (Release builds are okay...) #include <boost/property_tree/json_parser.hpp> When I say a "compiler error" I'm not referring to one of the usual CXXXX messages - what happens is this:- >INTERNAL COMPILER ERROR in 'C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30037\bin\HostX86\x64\CL.exe' > Please choose the Technical Support command on the Visual C++ > Help menu, or open the Technical Support help file for more information >Done building project "ardour.vcxproj" -- FAILED. >========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Just wondering if anyone else has encountered this..? Thanks, John

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