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[multi_index_container] Using equal_range with hashed indices
by Muruganand Karthikeyan 28 Sep '15

28 Sep '15

Hello! std::equal_range requires that the container be pre-sorted ( http://www.cplusplus.com/reference/algorithm/equal_range/) How does multi-index container handle this scenario with respect to hashed non-unique indices. The reason I ask is since I'm facing a situation with equal_range. Please see below code - typedef bmi< UserIdEntry, indexed_by< hashed_non_unique<tag<id1_id2>, composite_key<UserIdEntry, BMI_MEMBER(UserIdEntry, std::string, id1), BMI_MEMBER(UserIdEntry, std::string, id2) > > > > UserIdContainer; typedef UserIdContainer::index<id1_id2>::type IndexById1Id2; typedef IndexById1Id2::const_iterator IndexById1Id2_it; std::pair<IndexById1Id2_it, IndexById1Id2_it> entries = indexById1Id2.equal_range(make_tuple(id1_val, id2_val)); I'm seeing that *sometimes* entries.first equals indexById1Id2.end() and entries.second does not equal indexById1Id2.end(). The lookup is valid - meaning I've verified that there is at-least one entry which should be caught by the equal_range. I'm guessing the iterators' values are swapped. (second should be pointing to first and first should be pointing to second) What could be the reason for this? Thanks, MK.

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[multi_index_container] Using modify_key vs modify
by Muruganand Karthikeyan 28 Sep '15

28 Sep '15

Hello! Under what circumstances should we use modify_key? I believe we can achieve the same result using modify, so what is the advantage in using modify_key? Thanks, MK. -- Anand's signature

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Crash in managed_shared_memory
by Abhishek Kumar Pandey 28 Sep '15

28 Sep '15

Hi, I am using managed_shared_memory in my program. The program runs fine if only one instance is used. However if more than one instance is used then one instance dies randomly. The instance dies at the following code : char_string key_object(keyHashStr.c_str(), alloc_inst3); The sample program is : ----------------------- #include <boost/interprocess/managed_shared_memory.hpp> #include <boost/interprocess/allocators/allocator.hpp> #include <boost/interprocess/containers/string.hpp> #include <string> #include <iostream> #define RESERVED_BUFFER_SIZE_WRITE (8 * 0x0100000) namespace bip = boost::interprocess; //Typedefs of allocators and containers typedef bip::allocator<char, bip::managed_shared_memory::segment_manager> char_allocator; typedef bip::basic_string<char, std::char_traits<char>, char_allocator> char_string; int main() { bip::managed_shared_memory m_sharedMemUsage(bip::open_or_create, "MyBookkeeper", 2 * RESERVED_BUFFER_SIZE_WRITE); char_allocator alloc_inst3(m_sharedMemUsage.get_segment_manager()); for (int count = 0; count < 100000; ++count) { char_string key_obect("AAAAAAAAAAAAAAAAAAAAAAA", alloc_inst3); } } ----------------------- Please let me know if I am missing something in this program. Regards, Abhishek

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annoying warnings with mingw-w64 gcc-5.2.0
by renaud lepere 27 Sep '15

27 Sep '15

When I compile my code with gcc version 5.2.0 (x86_64-posix-seh-rev0, Built by MinGW-W64 project), I have annoying warnings with boost/utf and boost/asio (1.59). For example if I compile this simple file : #define BOOST_TEST_MODULE ExactSuite #include "boost/test/unit_test.hpp" I get : c:\Users\Renaud\nest\external\boost_1_59_0/boost/test/unit_test_log.hpp:130:28: warning: 'boost::unit_test::{anonymous}::unit_test_log' defined but not used [-Wunused-variable] BOOST_TEST_SINGLETON_INST( unit_test_log ) I can add #pragma GCC diagnostic ignored "-Wunused-variable" just before the include but it seems strange (and I have to do it in few other files). Does someone have similar problem ? or a better fix ?

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Become a Library Maintainer
by Alex Olivas 27 Sep '15

27 Sep '15

Hey All, This was just announced this week at CppCon (originally proposed at C++Now, by Robert Ramey). There's a new program and process to allow teams, who may be maintaining boost libraries internally, to become official maintainers. These are libraries that are currently being maintained by the Boost Community Maintenance Team (https://svn.boost.org/trac/boost/wiki/CommunityMaintenance) : * Boost.ConceptCheck * Boost.DateTime * Boost.DisjointSet * Boost.DynamicBitset * Boost.Format * Boost.Function * Boost.Logic * Boost.MPL * Boost.PropertyMap * Boost.Signals (which is deprecated) * Boost.Tokenizer More information about the program can be found here: http://beta.boost.org/community/official_library_maintainer_program.html If you're interested in becoming a Boost Library Official Maintiner, please send me an email. Thanks, Alex.

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[Boost-announce] Compile and run Boost examples online
by Antony Polukhin 25 Sep '15

25 Sep '15

Hi all, I've just launched the beta version of online examples for the "Boost Application Development Cookbook": http://apolukhin.github.io/Boost-Cookbook-4880OS/ There you can do online compilation of Boost related code, run examples, freely experiment with code from the book, read intros for the code and play around with the Boost libraries. I hope the site would be useful! P.S.: If you wish to report an error or wish to have some functionality added to the site, use the "Issues" link at https://github.com/apolukhin/Boost-Cookbook-4880OS or even make a pull request. P.P.S.: Intros for Chapters 7-12 are missing at this moment. I'll add them in a few months, sorry for the delay. -- Best regards, Antony Polukhin

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switch_
by MM 25 Sep '15

25 Sep '15

I see Boost.Switch_ was provisionally accepted back inJan 2008. I see some doc here: http://dancinghacker.com/switch But I can't see it released in recent boost versions I need to select a type to dynamic_cast to based on a runtime index, so I would have the type in a mpl::vector, and use the switch_ to pick up the right type? I have under 20 types. in pseudo c++11: void f(std::size_t i, const T* obj) { typedef mpl::vector<T0, .... Tn> alltypes_t; const auto* drvobj = dynamic_cast<...>(obj); /// what do I set as arg of dynamic_cast } If switch_ can help, where do I get the code for it? Rds,

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spirit help: segfault
by Littlefield, Tyler 25 Sep '15

25 Sep '15

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello all: I'm getting a segfault when I run this. It looks like the debug prints, but when I debug it I just get an endless loop of backtrace. If anyone can help point me in the right direction, I'd appreciate it. I'd also appreciate, if possible any tips/tricks for cleaning up this grammar. Thanks! //code here: /*** *I-EBNF parser * *This defines a grammar for BNF. */ //Speeds up compilation times. //This is a relatively small grammar, this is useful. #define BOOST_SPIRIT_NO_PREDEFINED_TERMINALS #define BOOST_SPIRIT_QI_DEBUG #include <boost/config/warning_disable.hpp> #include <boost/spirit/include/qi.hpp> #include <boost/spirit/include/phoenix_operator.hpp> #include <boost/fusion/adapted.hpp> #include <boost/fusion/support.hpp> #include <vector> #include <string> #include <iostream> namespace Parser { namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; enum class RHSType { Terminal, Identifier }; struct RHS { RHSType type; std::string value; }; struct Rule { std::string identifier; //lhs std::vector<RHS> rhs; }; } //expose our structs to fusion: BOOST_FUSION_ADAPT_STRUCT( Parser::RHS, (Parser::RHSType, type) (std::string, value) ) BOOST_FUSION_ADAPT_STRUCT( Parser::Rule, (std::string, identifier) (std::vector<Parser::RHS>, rhs) ) namespace Parser { typedef std::vector<Rule> RuleList; //our grammar definition template <typename Iterator> struct Grammar: qi::grammar<Iterator, std::list<Rule>, ascii::space_type> { Grammar(): Grammar::base_type(rules) { qi::char_type char_; letter = char_("a-zA-Z"); digit = char_('0', '9'); symbol = char_('[') | ']' | '[' | ']' | '(' | ')' | '<' | '>' | '\'' | '\"' | '=' | '|' | '.' | ',' | ';'; character = letter | digit | symbol | '_'; identifier = letter >> *(letter | digit | '_'); terminal = (char_('\'') >> character >> *character >> char_('\'')) | (char_('\"') >> character >> *character >> char_('\"')); lhs = identifier; rhs = terminal | identifier | char_('[') >> rhs >> char_(']') | char_('{') >> rhs >> char_('}') | char_('(') >> rhs >> char_(')') | rhs >> char_('|') >> rhs | rhs >> char_(',') >> rhs; rule = identifier >> char_('=') >> rhs; rules = rule >> *rule; } private: qi::rule<Iterator, char(), ascii::space_type> letter, digit, symbol, character; qi::rule<Iterator, std::string(), ascii::space_type> identifier, lhs, terminal; qi::rule<Iterator, RHS, ascii::space_type> rhs; qi::rule<Iterator, Rule, ascii::space_type> rule; qi::rule<Iterator, std::list<Rule>, ascii::space_type> rules; }; } int main() { Parser::Grammar<std::string::const_iterator> parser; boost::spirit::ascii::space_type space; std::string input; std::vector<std::string> output; bool result; while (std::getline(std::cin, input)) { if (input.empty()) { break; } std::string::const_iterator it, itEnd; it = input.begin(); itEnd = input.end(); result = phrase_parse(it, itEnd, parser, space, output); if (result && it == itEnd) { std::cout << "success" << std::endl; } } return 0; } - -- Take care, Ty twitter: @sorressean web:http://tysdomain.com pubkey: http://tysdomain.com/files/pubkey.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBAgAGBQJWBJSYAAoJEAdP60+BYxejpMwH/0EeVKIALYQOdl9esFIe9fIX JSor6vD/xn3e+L93TcsfpCSgtJiITfGgCPIURVX4FAE1Tf7PZSsd5lvQS6MgjyhQ q1EjDaAZNVt+cQhAftCoGcOPElx2aJXhNy/aTzcQqW1ui72t780GrF+MCo3tdq8p 5wIePhVbk0Gq8f3WBVGRXsKLi0hzwAPNXdHndNdYklNndKvClfHN8cwAZa5rFbMN b9eULQNtw42oT9tABAtpTfCl+tvExL3DMftXoALP5wONSv3ewjX8vNVWb5iv0XeZ yaYxLlnAGF314NgXOZKrtnXumDofnIzMDCZKxYFH+UfZfA7eFobGKOF3t/pN1JQ= =gD3u -----END PGP SIGNATURE-----

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slow gunzip
by Andy C 24 Sep '15

24 Sep '15

Hi, I am trying to write a simple program which processes large gziped files as streams. However, it turns out, that for some reason reading is very slow and it takes almost 10 times more to even count single lines as compared to a Java equivalent or "gunzip -c largefile.gz | wc -l". I would like to ask experts to point out what assumption I make. The source is attached below. Thanks in advance, Andy #include <iostream> #include <fstream> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/gzip.hpp> int main(int argc, char** argv) { char buf[10*4096]; std::cout << argv[1] << '\n'; long c=0; std::ifstream file(argv[1], std::ios_base::in | std::ios_base::binary); file.rdbuf()->pubsetbuf(buf, 10*4096); try { boost::iostreams::filtering_istream in; in.push(boost::iostreams::gzip_decompressor()); in.push(file); for(std::string str; std::getline(in, str); ) c++; } catch(const boost::iostreams::gzip_error& e) { std::cout << e.what() << '\n'; } std::cout << c << '\n'; return 0; }

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any_cast and added low-level const -> throws
by nice sw123 23 Sep '15

23 Sep '15

Hi, can anyone explain why an any_cast that adds a low-level const throws?? Example: char str[] = "a2"; boost::any ay(str); boost::any_cast<const char*>(ay); // throws, since a const is added!!! The only way to do this (without throwing), seems to be: boost::any_cast<char*>(ay); But why this mild "design deficiency"?? I call it "design deficiency", since the following is legal and works: char str2[] = "str2"; static_cast<const char *>(str2); So we should be able to add a low-level const, to make something read-only, right. Thanks for comments and explanations. n. Here's some test-code: /////// #include <iostream> #include <algorithm> #include <boost/any.hpp> int main() { char str[] = "a1"; boost::any ay(str); std::cout << "1 -- " << boost::any_cast<char *>(ay) << std::endl; strcpy(str, "a2"); /* throws!! */ //std::cout << "2 -- " << boost::any_cast<const char*>(ay) << std::endl; strcpy(str, "a3"); std::cout << "3 -- " << *boost::any_cast<char *>(&ay) << std::endl; strcpy(str, "a4"); /* segfault!! */ //std::cout << "4 -- " << *boost::any_cast<const char *>(&ay) << std::endl; char str2[] = "str2"; std::cout << "str2 -- " << static_cast<const char *>(str2) << std::endl; return 0; } ///////

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