July 2017 - Boost-users - lists.preview.boost.org

Boost Regex Back Reference Issue
by Nick 14 Jul '17

14 Jul '17

According to the Boost documentation for Back references (http://www.boost.org/doc/libs/1_64_0/libs/regex/doc/html/boost_regex/syntax…) which seems to be the same at least from 1.37 - 1.64. Quoting a piece of the documentation: ----- For example the expression: ^(a*).*\1$ Will match the string: aaabbaaa But not the string: aaabba ----- I'm finding two issues with the example cited. 1. It seems to me that the example of the string which should not match, should actually match. Ultimately, shouldn't the engine match the marked sub-expression with the first 'a' in order to satisfy the backreference? I tested this example with Oniguruma and with PHP's PCRE and they both matched the string noted here to not match. But also, since the marked sub-expression is (a*) then I wonder what the behavior would be if it couldn't make a match on 'a', since the '*' will allow for zero matches. In fact, it seems like everything in the pattern is effectively "optional" due to the '*' operator. I'm a novice with Perl, but unless I made a mistake, it will match unconditionally: print "It matches\n" if "aaabba" =~ /^(a*).*\1$/; It matches print "It matches\n" if "aaabbac" =~ /^(a*).*\1$/; It matches print "It matches\n" if "" =~ /^(a*).*\1$/; It matches print "It matches\n" if "x" =~ /^(a*).*\1$/; It matches print "It matches\n" if "xyz" =~ /^(a*).*\1$/; It matches print "It matches\n" if "123" =~ /^(a*).*\1$/; It matches 2. The other issue is that when I try this example with the string which is posted to not match, the Boost regex engine runs for a while and ultimately crashes with a memory error. (seems like it might be an endless loop of some sort). Is that a bug? Nick

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boost::unordered_map takes too long when I have only two elements in it
by Ram 14 Jul '17

14 Jul '17

Hi, I am using a boost::unordered_set but I sometimes have just two elements in it. It takes a long time then. Is it wrong if I have too few elements? Thanks, Ram

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rational - 1.64 version shear?
by Nicholas Devenish 14 Jul '17

14 Jul '17

With boost/rational.hpp, the code: boost::rational<int> a{1}; long b{1}; auto c{a * b}; Works fine up to 1.63.0, but fails to compile in 1.64+ on the multiplication with "error: invalid operands to binary expression". This seems to be due to some restructuring that changed the way multiplications are declared, which (as far as I can tell), meant the operation declaration became conditional on number of representable digits. This breaking change isn't listed on the release notes or the ::rational documentation, so I'm wondering if it was accidental and therefore a bug (whose behaviour might change), or a deliberate change to prevent downcasting and just undocumented? Nick (I've come onto a project stuck on 1.56 and trying to update it)

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⁨[process] problem with boost::process::on_exit
by Sandy Martel 14 Jul '17

14 Jul '17

The code below outputs: 1- child about to sleep for 2s 2- child about to sleep for 4s 3- child finish sleeping for 2s 6- sleep 4s child finished 5- child finish sleeping for 4s 4- sleep 2s child finished in a posix environment. I would expect the output to be in-order, looks like I get the wrong on_exit notification for the child processes I launch. Q: is this a bug or am I doing something wrong ? What is the correct way to get notified of specific process termination ? Regards, Sandy. code: #include <boost/process.hpp> #include <boost/asio.hpp> #include <thread> #include <iostream> int main( int argc, char **argv ) { if ( argc > 2 && strcmp( argv[1], "sleep" ) == 0 ) { auto s = atoi(argv[2]); std::cout << (s/2) << "- child about to sleep for " << s << "s" << std::endl; std::this_thread::sleep_for( std::chrono::seconds(s) ); std::cout << (s+1) << "- child finish sleeping for " << s << "s" << std::endl; return 0; } namespace bp = boost::process; boost::asio::io_service ios; // launch a child that will sleep for 2s auto c1 = bp::child( argv[0], "sleep", "2", ios, bp::on_exit( [](int, const std::error_code&) { std::cout << "4- sleep 2s child finished" << std::endl; }) ); // wait a bit, make sure the child startup for my test std::this_thread::sleep_for( std::chrono::milliseconds(10) ); // launch a child that will sleep for 4s auto c2 = bp::child( argv[0], "sleep", "4", ios, bp::on_exit( [](int, const std::error_code&) { std::cout << "6- sleep 4s child finished" << std::endl; }) ); // wait for the notifications ios.run(); }

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[serialization] "Archive" type turns into abstract class during save/load!
by r＠primef.actor 13 Jul '17

13 Jul '17

In a member load function function I call a static method that loads another archive file, i.e. something like this: ```c++ struct Bar; struct Foo { std::shared_ptr<Bar> data; template <class Archive> void load(Archive& archive, const unsigned /*version*/) { std::string key; archive >> key; data = Bar::loadSomewhere<Archive>(std::move(key)); } }; struct Bar { template <class Archive> std::shared_ptr<Bar> loadSomewhere(std::string key) { std::ifstream input(key); Archive ar(input); std::shared_ptr<Bar> bar(new Bar()); ar >> *bar; return bar; } }; ``` The problem is that `Bar::loadSomewhere` is passed a `boost::archive::polymorphic_iarchive`, while I invoke the serialization library with a `boost::archive::xml_iarchive`. This is an abstract class, so I can't instantiate it! So somewhere down the road the `xml_iarchive` is turned into a `polymorphic_iarchive`. I would like to prevent this from happening, because I instantiate an `Archive` object in the `Bar::loadSomewhere` function. How can I get around this problem?

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Re: [Boost-users] Boost 1.65.0 Beta 1 Release Candidate 2
by Matthieu Brucher 11 Jul '17

11 Jul '17

This happens a lot when people develop on gcc or visual studio and then try building with clang. Having a function and a class with the same name is bound to generate errors. So properly should be tagged as a bug. Le 11 juil. 2017 11:14 AM, "Raffi Enficiaud via Boost-users" < boost-users(a)lists.boost.org> a écrit : Le 11.07.17 à 02:14, Marshall Clow via Boost-users a écrit : The second release candidates for the 1.65.0 beta release are now > available at: > > > https://dl.bintray.com/boostorg/beta/1.65.0.beta.1/source/ > boost_1_65_0_beta1_rc2.7z > > https://dl.bintray.com/boostorg/beta/1.65.0.beta.1/source/ > boost_1_65_0_beta1_rc2.tar.bz2 > > https://dl.bintray.com/boostorg/beta/1.65.0.beta.1/source/ > boost_1_65_0_beta1_rc2.tar.gz > > https://dl.bintray.com/boostorg/beta/1.65.0.beta.1/source/ > boost_1_65_0_beta1_rc2.zip > > The SHA256 checksums are as follows: > > d54d29568c4e4933cbfe40a292b6cb84a7f68121e34f6a83f7d0f7c652b6b2d8 > boost_1_65_0_beta1_rc2.7z > 092676557513e992347d30dd0cd058fb8af2a401e5da4f4413f5b577852d726b > boost_1_65_0_beta1_rc2.tar.bz2 > 31fa3c807e2205e18f7d5c74f77f540677f7b0937af1e37f595c137e1e87bf84 > boost_1_65_0_beta1_rc2.tar.gz > 83c8d8b76fa9591572226a1a49fd191d76db3011b52b907cbbc8d37d46213bd2 > boost_1_65_0_beta1_rc2.zip > > > This RC contains a single fix to the stacktrace library. > > 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. > > Thanks! > > -- The release managers > Hi, I have this error during the build on OSX. Built with: ./b2 cxxflags="-std=c++11 -stdlib=libc++" linkflags="-stdlib=libc++" --without-log --layout=versioned install ...on 14200th target... common.mkdir bin.v2/libs/fiber/build/darwin-4.2.1/release/threading-multi common.mkdir bin.v2/libs/fiber/build/darwin-4.2.1/release/threading- multi/numa darwin.compile.c++ bin.v2/libs/fiber/build/darwin-4.2.1/release/threading- multi/numa/pin_thread.o libs/fiber/src/numa/pin_thread.cpp:23:10: warning: pin_thread() not supported [-W#pragma-messages] # pragma message "pin_thread() not supported" ^ 1 warning generated. darwin.compile.c++ bin.v2/libs/fiber/build/darwin-4.2.1/release/threading- multi/numa/topology.o libs/fiber/src/numa/topology.cpp:23:10: warning: topology() not supported [-W#pragma-messages] # pragma message "topology() not supported" ^ libs/fiber/src/numa/topology.cpp:27:14: error: use of undeclared identifier 'topology'; did you mean 'fibers::numa::topology'? std::vector< topology > topology() { ^~~~~~~~ fibers::numa::topology ./boost/fiber/numa/topology.hpp:38:21: note: 'fibers::numa::topology' declared here std::vector< node > topology(); ^ libs/fiber/src/numa/topology.cpp:27:14: error: template argument for template type parameter must be a type std::vector< topology > topology() { ^~~~~~~~ /Applications/Xcode8.1.app/Contents/Developer/Toolchains/Xco deDefault.xctoolchain/usr/bin/../include/c++/v1/vector:456:17: note: template parameter is declared here template <class _Tp, class _Allocator = allocator<_Tp> > ^ 1 warning and 2 errors generated. "g++" -ftemplate-depth-128 -O3 -Wall -dynamic -gdwarf-2 -fexceptions -Wno-inline -fPIC -arch x86_64 -std=c++11 -stdlib=libc++ -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_DYN_LINK=1 -DBOOST_DISABLE_ASSERTS -DBOOST_FIBERS_DYN_LINK=1 -DBOOST_FIBERS_SOURCE -DBOOST_FILESYSTEM_DYN_LINK=1 -DBOOST_SYSTEM_DYN_LINK=1 -DNDEBUG -I"." -c -o "bin.v2/libs/fiber/build/darwin-4.2.1/release/threading-multi/numa/topology.o" "libs/fiber/src/numa/topology.cpp" ...failed darwin.compile.c++ bin.v2/libs/fiber/build/darwin -4.2.1/release/threading-multi/numa/topology.o... _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org https://lists.boost.org/mailman/listinfo.cgi/boost-users

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Boost 1.65.0 Beta 1 Release Candidate 1
by Marshall Clow 09 Jul '17

09 Jul '17

The release candidates for the 1.61.0 release are now available at: https://dl.bintray.com/boostorg/beta/boost_1_65_0_beta1_rc1.7z https://dl.bintray.com/boostorg/beta/boost_1_65_0_beta1_rc1.tar.bz2 https://dl.bintray.com/boostorg/beta/boost_1_65_0_beta1_rc1.tar.gz https://dl.bintray.com/boostorg/beta/boost_1_65_0_beta1_rc1.zip The SHA256 checksums are as follows: cd7429340bb4aae38e0ad2e9f59c39e66335302c41577956123e55fc1e2a28ee boost_1_65_0_beta1_rc1.7z fda076f7b3c994524d9cd41926c72f4a9b7c017bef310a055956fdd0bed7c358 boost_1_65_0_beta1_rc1.tar.bz2 0d1473041f7a9fa9ce1e256c870cc52af6f98abf723cf4f1ac61c2b45f45d38a boost_1_65_0_beta1_rc1.tar.gz f45bbb75b84cdc0c66f8a571d77c518cfbac076d7a6fc7937c4812f0f242a792 boost_1_65_0_beta1_rc1.zip 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. Thanks! -- The release managers

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building for msvc-14.1
by Isaac Lascasas 09 Jul '17

09 Jul '17

Hello I have serious problems building boost for vs2017. My win10 install has just visual studio community 2017 installed right now, with windows SDK 10.0.15063.0 and 8.1. I run the vs2017 x64 native prompt and then I do something like this: b2 -j12 toolset=msvc-14.1 address-model=64 architecture=x86 link=static threading=multi runtime-link=shared --build-type=minimal stage --stagedir=stage/x64 some headers give weird stl container errors: c:\libs\boost_1_64_0__64\boost/archive/detail/basic_serializer_map.hpp(47): error C2039: 'set': is not a member of 'std' Thanks, Isaac.

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[review] Mp11 review starts in one week
by Bjorn Reese 08 Jul '17

08 Jul '17

The formal review of Peter Dimov's Mp11 library is scheduled for July 15 - July 24, 2017 [1]. Mp11 is a C++11 metaprogramming library for compile-time manipulation of data structures that contain types. It’s based on template aliases and variadic templates and implements the approach outlined in the article "Simple C++ metaprogramming" [2] and its sequel [3]. These articles are useful background information for the review. * Mp11 aims to make simple usage simple, and to support complex usage without complicating the simple use cases. * Mp11 works on any type-list, whether its own type-list mp_list, or standard type-lists such as std::tuple and std::variant, or user-defined type-lists. * Mp11 works with any meta-function, such as C++11 or Boost type-traits, or user-defined type-traits. Mp11 can be found here: * Documentation: https://rawgit.com/pdimov/mp11/master/doc/html/mp11.html * Source code: https://github.com/pdimov/mp11/tree/master [1] http://www.boost.org/community/review_schedule.html [2] http://pdimov.com/cpp2/simple_cxx11_metaprogramming.html [3] http://pdimov.com/cpp2/simple_cxx11_metaprogramming_2.html

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Serialization support for small_vector
by Brian Wood 07 Jul '17

07 Jul '17

Shalom I've added support for small_vector to the C++ Middleware Writer. While testing the support, I got a warning about dereferencing a type-punned pointer breaking strict-aliasing rules. That was on line 340 of small_vector.hpp. I was using g++ 7.1 on FreeBSD/ TrueOS. I used the following "Middle" code for testing: message-lengths variable example_messages -out (message_id_8, ::boost::container::small_vector<int32_t,30>) -in (::boost::container::small_vector<int32_t,30>) } >From what I could tell the serialization/deserialization worked fine. If small_vector were broken out into a separate library that would be helpful from my perspective. It would make it easier for me to add small_vector to my example code. Brian Ebenezer Enterprises - In G-d we trust. http://webEbenezer.net

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