April 2018 - 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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[Test] Test executable crashes always
by Nate Widmyer 26 Jun '18

26 Jun '18

Hello, I've made some unit tests with boost test before without issue, but on my latest rather ordinary test, I've been able to get Boost test to crash the executable in debug and release mode when boost test is making a report before terminating. test_exe.exe!boost::unit_test::framework::get(unsigned long id, boost::unit_test::test_unit_type t) Line 1388 C++ test_exe.exe!boost::unit_test::framework::get<boost::unit_test::test_unit>(unsigned long id) Line 208 C++ test_exe.exe!boost::unit_test::results_reporter::make_report(boost::unit_test::report_level l, unsigned long id) Line 175 C++ test_exe.exe!boost::unit_test::unit_test_main(boost::unit_test::test_suite *(*)(int, char * *) init_func, int argc, char * * argv) Line 235 C++ test_exe.exe!main(int argc, char * * argv) Line 287 C++ That's the default report_level of 'confirm' If I use report_level=short or detailed, I get a similar crash: test_exe.exe!boost::unit_test::framework::get(unsigned long id, boost::unit_test::test_unit_type t) Line 1388 C++ test_exe.exe!boost::unit_test::framework::get<boost::unit_test::test_suite>(unsigned long id) Line 207 C++ test_exe.exe!boost::unit_test::traverse_test_tree(unsigned long id, boost::unit_test::test_tree_visitor & V, bool ignore_status) Line 365 C++ test_exe.exe!boost::unit_test::results_reporter::make_report(boost::unit_test::report_level l, unsigned long id) Line 185 C++ test_exe.exe!boost::unit_test::unit_test_main(boost::unit_test::test_suite *(*)(int, char * *) init_func, int argc, char * * argv) Line 235 C++ test_exe.exe!main(int argc, char * * argv) Line 287 C++ Here's the get() method: test_unit& get( test_unit_id id, test_unit_type t ) { test_unit* res = impl::s_frk_state().m_test_units[id]; BOOST_TEST_I_ASSRT( (res->p_type & t) != 0, internal_error( "Invalid test unit type" ) ); return *res; } Crash occurs on line 2 of the function. I logged 'res' each time the function is called and many times its valid, but when it runs this one test (by itself or with others), 'res' always ends up being NULL. id seems to always be '1', and t is TUT_ANY (17) if generating a confirmation report or TUT_SUITE (16) if generating a short or detailed report. If I use the option '--report_level=no', then execution does complete fine. I followed through on some process of elimination and it seems to be related to using a fixture? Having no test body still causes the crash. It wasn't until I removed the fixture (and its usage in the body of the test) did the executable not crash. I ensured that I was using the standard fixture model found here: http://www.boost.org/doc/libs/1_64_0/libs/test/doc/html/boost_test/tests_or… OS is Win 7 w/ VS2015 boost is 1.64.0 and was built with: b2 toolset=msvc-14.0 link=static runtime-link=static variant=debug address-model=64 --without-atomic --without-container --without-context --without-coroutine --without-coroutine2 --without-graph --without-graph_parallel --without-iostreams --without-locale --without-math --without-mpi --without-serialization --without-signals --without-type_erasure --without-wave -j4 --abbreviate-paths --without-python -d2 Any help would of something to look at or change would be appreciated. Thanks for your time, Nathan

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help
by Radekkostra＠seznam.cz 30 Apr '18

30 Apr '18

hello, i am trying to build boost, but i have problems. First is in log(bootstrap.log - could not find "vswhere") and second is when compiling boost(this command :.\b2 --toolset=msvc link=shared,static address -model=64 --with-system --with-filesystem -j 4(5 failed,12skipped,79 updated).

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[Process] Help needed with boost::process::extend::on_*
by Günter Berner 26 Apr '18

26 Apr '18

I am using boost::process::child to create a child process: boost::process::child child("foo"); This works fine so far (on Linux + Windows). Now i want to use a handler which is executed during the fork process: boost::process::child child("foo", boost::process::extend::on_setup = [](auto& exec) { // ... }); This also works fine - as long as a more or less up-to-date C++ compiler or C++ standard. Since g++-4.8.5 (which I have to use) does not support auto template deduction for lambdas, i have to replace the lambda parameter type with a concrete type. boost::process::child child("foo", boost::process::extend::on_setup = [](<WHAT_GOES_HERE?>& exec) { // ... }); Boost.Process documentation only uses the modern approach with auto template deduction. I simply cannot find an example/documentation where the concrete types are shown. Thanks.

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failed coversion
by Markel, Joseph 25 Apr '18

25 Apr '18

Is there a way to get the int value by performing division on boost::any variables? #include <boost/any.hpp> int main(void) { boost::any a = 10; std::cout << boost::any_cast<int>(a) << std::endl; boost::any s = 2.5; // scaling factor // scale the value a = boost::any_cast<int>(a)/boost::any_cast<float>(s); std::cout << boost::any_cast<int>(a) << std::endl; } This throws the error boost::bad_any_cast: failed conversion using boost::any_cast Thanks CONFIDENTIALITY NOTICE: This e-mail communication and any attachments may contain proprietary and privileged information for the use of the designated recipients named above. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.

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[multiprecision] static_cast<cpp_bin_float_100> gives strange values.
by Vögl, Christian 20 Apr '18

20 Apr '18

Hi everyone. The following Situation: I tried to improve the accuracy of a numerical function by replacing all double variables with cpp_bin_float_100. The parameters of this function contain two 3-element double arrays, which I convert to cpp_bin_float_100 by the following function: static void equal(cpp_bin_float_100* a, double* b) { for(int i=0; i<3;i++) { a[i]=static_cast<cpp_bin_float_100>(b[i]); } } the third element seems to be converted correctly, the first and second are totally off. (e. g. 100 -> 1.5625)

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[asio] Using struct ip_mreqn to joing multicast group
by Klebsch, Mario 20 Apr '18

20 Apr '18

Hi, I need to receive multicasts on multiple interfaces and handle them differently, depending on the network interface they arrived on. For each network interface, I create an UDP socket and I use Socket.set_option(boost::asio::ip::multicast::join_group(MCastReqAddr.to_v4(), LocalAddr.to_v4() ), ec); to join the multicast group. LocalAddr is the local IPv4 address of the interface. Unfortunately, I receive each incoming multicast message on each socket. I found, that boost::asio::ip::multicast::join_group uses struct ip_mreq, where the multicast address and the local address can be specified. On linux the man page on IP_ADD_MEMBERSHIP tells to use struct ip_mreqn. This structure had an additional member imr_ifindex. The documentation is not very clear about the difference between imr_address and imr_ifindex. So, I want to try it out and wonder, whether boost::asio supports using struct ip_mreqn for IP_ADD_MEMBERSHIP. If not, does anybody know, how to write my own class to be used with Socket.set_option? 73, Mario -- Mario Klebsch Actia I+ME GmbH Mario.klebsch(a)ime-actia.de<mailto:Mario.klebsch@ime-actia.de> Dresdenstrasse 17/18 Fon: +49 531 38 701 716 38124 Braunschweig Fax: +49 531 38 701 88 Germany

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Boost.Range and initializer_list
by Robert Jones 18 Apr '18

18 Apr '18

Hi All Does the Boost.Range library support initializer_list as a range type? I thought anything with begin() and end() methods was fair game, but this code doesn't work, unless I'm doing it wrong. #include <iostream> #include <vector> #include <boost/range/adaptor/reversed.hpp> int main( ) { using namespace std; using namespace boost::adaptors; vector<int> v { 1, 2, 3 }; for( int i : v | reversed ) { cout << i << " "; } // Ok for( int i : { 1, 2, 3 } | reversed ) { cout << i << " "; } // Bad } Kind Regards Rob.

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[Boost.Range] combine, native range-for, and destructuring
by John M. Dlugosz 18 Apr '18

18 Apr '18

I want to go through two vectors at the same time, and the way to do this is to "zip" the items from each into a tuple. boost::combine is a function for that. for (auto&[def,residue] : boost::combine(playdef, residues)) { gives me an error 1>e:\scratch\c++code\scratchproject2\fizzbuzz\fizzbuzz.cpp(66): error C2440: 'initializing': cannot convert from 'boost::tuples::cons<std::pair<int,std::string_view> &,boost::tuples::cons<int &,boost::fusion::detail::build_tuple_cons<boost::fusion::single_view_iterator<Sequence,boost::mpl::int_<1>>,Last,true>::type>>' to 'boost::tuples::cons<std::pair<int,std::string_view> &,boost::tuples::cons<int &,boost::fusion::detail::build_tuple_cons<boost::fusion::single_view_iterator<Sequence,boost::mpl::int_<1>>,Last,true>::type>> &' The only difference is in the final `&` character. Trying to explore the behavior in pieces, I try: for (auto row : boost::combine(playdef, residues)) { auto&[def, residue] = row; // line 1 row.get<1>() = 17; // line 2 residue= 42; // line 3 Now line2 does work, and I note that assignment goes through and updates the original `residues` vector. The destructuring on line 1 does compile now, being on a separate line. But line 3 gives me an error about not being able to assign to a crazy complicated type. What's going on? Is Boost.Range zipped ranges simply not compatible with the native language features?

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