January 2019 - Boost-users - lists.preview.boost.org

[interprocess] Determine size of managed_shared_memory
by Kai Benndorf 12 Oct '19

12 Oct '19

Hi all, I want to create a managed_shared_memory in exactly the size I needed. Therefore I do something like this: size = sizeof( common_managed_shared_memory ); size += sizeof( MyClassInSharedMem ); managed_shared_memory segment(create_only, "name", size ); MyClassInSharedMem allocates itself some memory by segment->allocate(). I added this also to the size, but get a boost::interprocess::bad_alloc exception on allocating this additional memory. Are there some magic bytes I forgot to add? Many thanks in advance Kai

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boost::filtered_graph filtering on vertex color... if I only had a colormap
by Brian Davis 19 Jul '19

19 Jul '19

Lets say I have a graph g (of type graph_t) and a color map (boy I wish I had a colormap): typedef boost::property_map<graph_t, boost::vertex_color_t>::type color_map_t; or is it? auto indexmap = boost::get(boost::vertex_index, g); auto colors = boost::make_vector_property_map<boost::default_color_type>(indexmap); or maybe? auto indexmap = boost::get(boost::vertex_index, g); auto colors = boost::make_vector_property_map<boost::vertex_color_t>(indexmap); or possibly some goop found on the internet? boost::make_iterator_property_map(color_map.begin(), boost::get(boost::vertex_index, data_->g), color_map[0]) or other internet goop? typedef boost::property_map<GraphType, boost::vertex_color_t>::type color_map_t; color_map_t colorMap; boost::color_map(colorMap)) or other internet goop?? std::vector<int> colorMap(num_vertices(g), boost::white_color); so confused... (certainly not surprised why bgl is not a part of stl) Can someone help explain the various types and ways of specifying colormaps and the logic for each way and means? and a function (if I could get that far without VS syntax highlighter going bonkers and gobs of compiler errors.. you know the type): make_pretty(g, colormap ) which colors the graph colormap and a filter struct for boost::filtered_graph<Graph, EdgePredicate, VertexPredicate> (where I wonder why if I only want to filter vertices I have to set boost::keep_all for EdgePredicate... sigh... I know the answer... and also know how long it found me to find/figure out boost::keep_all - and if you are looking for boost::keep_all and found it here... your welcome ;-) ) and modifying (probably incorrectly) boost::filtered_graph example to: template <typename ColorMap> struct vertex_color_filter_eq { vertex_color_filter_eq() { } vertex_color_filter_eq(ColorMap colormap/*, boost::default_color_type c*/) : m_colormap(colormap)/*, m_c(c)*/ { } template <typename Vertex> bool operator()(const Vertex& v) const { return 0 < get(m_colormap, v); //return c < get(m_colormap, v); } ColorMap m_colormap; //boost::default_color_type m_c; }; auto indexmap = boost::get(boost::vertex_index, g); auto colors = boost::make_vector_property_map<boost::default_color_type>(indexmap); // some where here I would call make_pretty(g, colors) typedef property_map<graph_t, boost::vertex_color_t>::type ColorMap_t; vertex_color_filter<ColorMap_t> filter(colors); // boost::filtered_graph<graph_t, boost::keep_all, VertexPredicate> boost::filtered_graph<graph_t, boost::keep_all, vertex_color_filter> fg(g, filter); // Later say if I could get it compile and better if it compiled and worked I could move on and auto color = boost::red_color; typedef property_map<graph_t, boost::vertex_color_t>::type ColorMap_t; vertex_color_filter<ColorMap_t> filter(colors, color); boost::filtered_graph<graph_t, boost::keep_all, vertex_color_filter> fg(g, filter); Maybe if I color them yellow, I can then reach the wizard pull back the curtain and ask how to create a color map... If I only had a color map.

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Question on Posix timezone string
by Mats Webjörn/WIKAB 10 Mar '19

10 Mar '19

I'm using Boost 1.66 and use the following code to get a Posix string to set my uCLinux TZ environment variable to get a local time from an UTC time #include <boost/date_time/local_time/tz_database.hpp> #include <boost/date_time/local_time/local_time.hpp> tz_database tz_db; tz_db.load_from_file("./date_time_zonespec.csv"); time_zone_ptr nyc = tz_db.time_zone_from_region("Europe/Stockholm"); auto s = nyc->to_posix_string(); // "CET+01CEST+01,M3.5.0/02:00,M10.5.0/03:00" setenv("TZ", s.c_str(), 1); The odd thing is that my localtime becomes incorrect, and is actually 1 hr wrong on the opposite side of UTC. But, when I read https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html it says "The offset specifies the time value you must add to the local time to get a Coordinated Universal Time value". Not add to UTC time, which seems like the Boost Posix string assumes !!!!! Which explains why 16:00 UTC give 15:00 CET instead of 17:00 which is the correct value, when using localtime_r(). Am I missing something fundamentally, or what? Regards Mats Webjörn Webjörn IngenjörsKonsult AB Solhemsbackarna 75A SE-163 56 SPÅNGA Sweden

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Boost Test thread safety
by Dan Field 21 Feb '19

21 Feb '19

Hi folks: I'm trying to identify whether or not the boost Test library is thread safe in the sense that multiple threads can simultaneously interact with the library's various macros and API. I'm more interested in a single test being multi-threaded than being able to run multiple test cases simultaneously. In early documentation of the Test library (version 1.58.0 and before) , there's a section in the introduction called "Open issues" that indicates that the library is not thread-safe. However, the documentation after 1.58.0 was substantially re-written, and I don't see any discussion regarding thread safety at all. The question remains. is the Test library thread-safe or not? If there is a definitive statement regarding this issue, please let me know. Thanks in advance!

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[boost.test] Colors
by Udo Steinbach 20 Feb '19

20 Feb '19

Ahoi! I use boost.test and have now updated to boost v1.68 on Windows, working in standard console. Now Test has colored output, YEAH. The result you see in the picture https://www2.pic-upload.de/img/36193998/no_error_detected.png Notice that I don't use the standard color scheme. With set BOOST_TEST_COLOR_OUTPUT=1 text is light green on gray, bad to read. set BOOST_TEST_COLOR_OUTPUT=0 does black on gray. After that the colors are set to my scheme. Now error result with set BOOST_TEST_COLOR_OUTPUT=1: https://www2.pic-upload.de/img/36193997/failure.png Light red on gray, OK to read, but reset to dark red on gray. I have to use the color command to reset the colors. With command line options it's all the same. Hmmm, how useful can colors be, if the standard output (no error detected) is only one short line? Both pics on https://www.pic-upload.de/gal-1197957/om664y/1.html -- Fahrradverkehr in Deutschland: http://radwege.udoline.de/ GPG: A245 F153 0636 6E34 E2F3 E1EB 817A B14D 3E7E 482E

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issue with property_tree/json_parser
by Harikrishna 29 Jan '19

29 Jan '19

Hi All, I am trying to use boost json_parser. I have included json_parser.hpp in my cpp file, I have not included any other code. But I am getting many compilation errors like error: 'boost::spirit::classic' has not been declared and In function void boost::property_tree::json_parser::read_json_internal(std::basic_istream<typename Ptree::key_type::value_type, std::char_traits<typename Ptree::key_type::value_type> >&, Ptree&, const std::string&): [exec] /usr/include/boost/property_tree/detail/json_parser_read.hpp:288: error: \u2018classic\u2019 is not a namespace-name Can you help me resolve this issue? -- Thanks Harikrishna

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[Spirit] Looking for a little Qi guidance for Unicode parsing
by Michael Powell 28 Jan '19

28 Jan '19

Hello, I am turning a corner in my JSON parser. I support ASCII through and through, but now I want to support Unicode, apparently UTF-8, part of the JSON standard. From what I can tell, this is not the entire grammar, but just for Strings. Looking for a little guidance on how to approach that issue, the elements involved, etc. Such as, are we talking about C++ std::wstring? I have also seen std::u32string referenced in some forums. To begin with, it is a somewhat naive impression, would the characters not translate to unsigned char or char, but rather to std::wstring::value_type or std::u32string::value_type? Things like that come to mind approaching the issue. Additionally, how to otherwise handle symbol tables such as escape characters, i.e. from: struct escapes_t : qi::symbols<char, char> { escapes_t() { this->add("\\b", '\b') ("\\f", '\f') ("\\n", '\n') ("\\r", '\r') ("\\t", '\t') ("\\v", '\v') ("\\\\", '\\') ("\\/", '/') ("\\'", '\'') ("\\\"", '"') ; } } char_esc; And on from there. Thanks! Best regards, Michael W Powell

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ASIO: Writing Composed Operations
by Cristian Morales Vega 26 Jan '19

26 Jan '19

Hi, I was looking at https://www.boost.org/doc/libs/develop/libs/beast/doc/html/beast/using_io/w… and came up with a question I can't answer: In https://github.com/boostorg/beast/blob/develop/example/echo-op/echo_op.cpp#… why does it use the AsyncStream associated executor without even looking at the potentially different (right?) Handler associated executor? Regards.

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Fwd: Help needed with include path
by David Aldrich 25 Jan '19

25 Jan '19

Hi I am using Boost on Ubuntu 18.04 LTS, which has boost 1.65.1 installed. I want to use boost 1.69, which I have installed on another server. I specify that remote boost path in my makefile and make compiles my source file with: g++ -c -Wall -m64 -I/net/simdata/OpenSourceLibs/Boost/rel-1.69.0/ -fpic -O3 SINRCalculation.cpp -o _gnuRelease/SINRCalculation.o Now that source file uses boost/multi_array.hpp. The above compiler command gives error: In file included from /usr/include/boost/multi_array.hpp:30:0, from SINRCalculation.cpp:25: /net/simdata/Hudson_OpenSourceLibs/Boost/rel-1.69.0/boost/type_traits.hpp:118:10: fatal error: boost/type_traits/is_nothrow_swappable.hpp: No such file or directory #include <boost/type_traits/is_nothrow_swappable.hpp> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. Now my copy of boost 1.69 does contain is_nothrow_swappable.hpp so, at first sight, that error is surprising. I think what is happening is the is_nothrow_swappable.hpp is being searched for on the system library path (boost 1.65 does not have that file), not the one I specified using -I. Am I correct? If so, how can I force the compiler to use the boost 1.69 path consistently for all paths?

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Memory mapped files
by Simon Giddings 24 Jan '19

24 Jan '19

Good morning, We are developing a system which heavily uses memory mapped files. These files are initially created under a unix system, but will then be used in portable systems such as Android and iOS. We are having some problems loading memory mapped files created under Unix into Android. Is this scenario even possible ? Are the memory mapped files compatible between systems ? Hope you will be able to shed some light on this. Best regards Simon

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