January 2015 - 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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[Range, Phoenix] What am I missing...
by Robert Jones 25 Apr '17

25 Apr '17

Hi Folks Can anyone explain the output of this program... #include <iostream> #include <boost/range/algorithm/copy.hpp> #include <boost/range/counting_range.hpp> #include <boost/range/adaptor/reversed.hpp> #include <boost/range/adaptor/transformed.hpp> #include <boost/phoenix/bind/bind_function.hpp> #include <boost/phoenix/core/argument.hpp> int f( int i ) { return i * 2; } int main( ) { using boost::adaptors::reversed; using boost::adaptors::transformed; using boost::counting_range; using boost::copy; using boost::phoenix::arg_names::_1; copy( counting_range( 1, 5 ) | reversed | transformed( f ), std::ostream_iterator<int>( std::cout, " " ) ); std::cout << std::endl; copy( counting_range( 1, 5 ) | reversed | transformed( bind( f, _1 ) ), std::ostream_iterator<int>( std::cout, " " ) ); std::cout << std::endl; } Which is... 8 6 4 2 1768406272 1768406272 1768406272 1768406272 I'm using Gcc 4.6.2 & Boost 1.53 Thx All.

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[statechart] Passing parameters from event to State Local Storage
by Christophe Bourez 16 Nov '16

16 Nov '16

I need to maintain a parameter into the state local storage. This parameter is initially contained in the event that causes the transition to the target state. I give hereafter a small illustrative example. typename sc = boost::statechart; class EvTest : public sc::event<EvTest> { public: EvTest(std::size_t val) : value(val) {} std::size_t getValue() const { return this->value; } private: std::size_t value; }; class MyStateMachine; class StSource; class StTarget; class StSource : public sc::simple_state<StSource, MyStateMachine> { public: typedef sc::custom_reaction<EvTest> reactions; sc::result react(const EvTest &event) { // How to pass event.getValue() to the target state ? transit<StTarget>(); } }; class StTarget : public sc::simple_state<StTarget, MyStateMachine> { public: StTarget(std::size_t val) : val(value) {} private: std::size_t value; }; Thanks, Christophe

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Some strange boost headers errors
by alfonso santimone 15 May '15

15 May '15

Hi guys, i'm a boost newbie. I've got to include boost libraries in the include path of a VisualStudio 2012 project. When i try to compile i have all these errors. Every errors is related to missing headers ( boost ones and even standard Win ones ) and to synthax errors depending on missing headers i guess. Do someone have any idea on what's wrong here? I just post here a few lines of errors, but the other ones are all of the same kind Error 1 error C2061: syntax error : identifier 'boost' C:\boost_1_57_0\boost\core\ checked_delete.hpp 24 1 csound~ Error 2 error C2059: syntax error : ';' C:\boost_1_57_0\boost\core\checked_delete.hpp 24 1 csound~ Error 3 error C2449: found '{' at file scope (missing function header?) C:\boost_1_57_0\boost\core\checked_delete.hpp 25 1 csound~ Error 4 error C2059: syntax error : '}' C:\boost_1_57_0\boost\core\checked_delete.hpp 67 1 csound~ Error 5 error C2054: expected '(' to follow 'using' C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\cstddef 19 1 csound~ Error 6 error C2061: syntax error : identifier 'using' C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\cstddef 19 1 csound~ Error 7 error C2061: syntax error : identifier 'boost' C:\boost_1_57_0\boost\smart_ptr\detail\sp_nullptr_t.hpp 23 1 csound~ Error 8 error C2059: syntax error : ';' C:\boost_1_57_0\boost\smart_ptr\detail\sp_nullptr_t.hpp 23 1 csound~ Error 9 error C2449: found '{' at file scope (missing function header?) C:\boost_1_57_0\boost\smart_ptr\detail\sp_nullptr_t.hpp 24 1 csound~ Error 10 error C2059: syntax error : '}' C:\boost_1_57_0\boost\smart_ptr\detail\sp_nullptr_t.hpp 41 1 csound~ Error 11 error C2054: expected '(' to follow 'using' C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\cstdlib 19 1 csound~ Error 12 error C2061: syntax error : identifier 'using' C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\cstdlib 19 1 csound~ Error 13 error C2061: syntax error : identifier 'abort' C:\Program Files (x86)\Microsoft Visual Studio many thanks in advance bests alfonso www.elgallorojorecords.com soundcloud.com/alfonsosantimone www.facebook.com/alfonsosantimone

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Re: [Boost-users] lexical_cast between double and string slow in Visual Studio 2013
by David Roberts 07 May '15

07 May '15

> That issue is unknown. I'd really appreciate the investigation. I have done some more investigation, and there are two factors that only cause the slowness when they both occur together. > Try excluding the lexical_cast from test, I have a feeling that this is only MSVC related issue: > > #include <sstream> > #include <string> > > int main (int, char **) > { > for (double count = 0.0; count < 1000000.0; count += 1.41) > { > std::stringstream ss; > ss << count; > std::string result = std::move(ss.str()); > ss.str(std::string()); > > ss << result; > ss >> count; > } > > return 0; > } > Running your test program does not exhibit the problem. It runs in around 3 seconds on my machine when built with either Visual Studio 2010 or Visual Studio 2013. However, changing it very slightly to match more closely what lexical_cast does internally does recreate the problem: #include <sstream> #include <string> int main (int, char **) { for (double count = 0.0; count < 1000000.0; count += 1.41) { std::stringstream ss; ss.unsetf(std::ios::skipws); ss.precision(17); ss << count; std::string result = std::move(ss.str()); ss.str(std::string()); ss << result; ss >> count; } return 0; } The effect of setting the precision to 17 is that lots of 9s appear in the string representations. (The number 17 is what boost::detail::lcast_get_precision(double*) chooses.) Without the precision call the contents of the string called result start off like this: 0 1.41 2.82 4.23 5.64 7.05 8.46 9.87 11.28 12.69 With precision set to 17 they start off like this: 0 1.4099999999999999 2.8199999999999998 4.2299999999999995 5.6399999999999997 7.0499999999999998 8.4599999999999991 9.8699999999999992 11.279999999999999 12.69 This happens for both Visual Studio 2010 and Visual Studio 2013. Then the next difference is that Visual Studio 2013 spends a lot longer handling all the extra 9s. Changing the program so that the double is converted to a string using std::stringstream without a precision call and then back to double using lexical_cast takes about 3 seconds for both Visual Studio 2010 and Visual Studio 2013. It is the combination of having all the extra 9s to parse and using Visual Studio 2013 that makes the test using lexical_cast to go both ways slow. Both Visual Studio 2010 and Visual Studio 2013 do the conversion by calling std::num_get<char,std::istreambuf_iterator<char,std::char_traits<char> > >::do_get() which then calls a function called _Stodx() which is implemented in xstod.c. This function is very different for the two versions. In Visual Studio 2010 it's a relatively thin wrapper around the C function strtod(). In Visual Studio 2013 _Stodx() has got a completely new implementation that's generated by #including xxstod.h with some macros defined. The original C function strtod() is much faster than the new _Stodx() when there are lots of 9s at the end of the strings being parsed. This modification to the program: #include <sstream> #include <string> #include <stdlib.h> int main (int, char **) { for (double count = 0.0; count < 1000000.0; count += 1.41) { std::stringstream ss; ss.unsetf(std::ios::skipws); ss.precision(17); ss << count; std::string result = std::move(ss.str()); ss.str(std::string()); ss << result; char *endptr; count = strtod(ss.str().c_str(), &endptr); } return 0; } has a runtime of about 3 seconds even though it's got to cope with all the 9s. I guess only someone from Microsoft or Dinkumware could comment on why _Stodx() was reimplemented. But the other thing is that by setting precision to 17 lexical_cast is bloating the string representations of the doubles with lots of 9s in both Visual Studio 2010 and Visual Studio 2013. Setting precision to 15 instead prevents this, and makes the original test run faster even with Visual Studio 2013 (about 4 seconds rather than 10). Regards, David

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[boost.geometry] buffer distance strategies
by gchlebus 09 Mar '15

09 Mar '15

Hi, I am wondering whether it would be possible to achieve anisotropic buffering (distances in neg x, pos x, neg y, pos y can have different values) of a polygon using the buffer function with custom-implemented distance strategy. What I want to achieve is presented on the figure 2-b in the following paper: http://itcnt05.itc.nl/agile_old/Conference/mallorca2002/proceedings/posters… I would be grateful to hear from you whether it is doable, and if positive, how one could implement such a custom distance strategy. Best, -- View this message in context: http://boost.2283326.n4.nabble.com/boost-geometry-buffer-distance-strategie… Sent from the Boost - Users mailing list archive at Nabble.com.

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Statechart serialization
by mbrodeur65 04 Mar '15

04 Mar '15

Hi, I'm looking for a solution to serialize boost::statechart objects. I'm aware that this feature is on the statechart library todo list but was wondering if there are any workaround to achieve this with the latest boost release (1.34) ? thanks for your help ! mbrodeur65 -- View this message in context: http://www.nabble.com/Statechart-serialization-tf4131326.html#a11749139 Sent from the Boost - Users mailing list archive at Nabble.com.

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problems building
by Nathan Ridge 28 Feb '15

28 Feb '15

Hi list, I'm trying to build Boost for the first time in a while, and getting unexpected errors. I have a git checkout of the 'master' branch, but I've also tried with the 'boost-1.57.0' tag and had the same problem. The build command I'm running is './b2 --with-filesystem', and the errors I'm getting are of the following form: gcc.compile.c++ bin.v2/libs/system/build/gcc-4.9.0/release/threading-multi/error_code.o In file included from libs/system/src/error_code.cpp:16:0: ./boost/system/error_code.hpp:18:39: fatal error: boost/utility/enable_if.hpp: No such file or directory #include <boost/utility/enable_if.hpp> ^ compilation terminated. "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -pthread -fPIC -DBOOST_ALL_NO_LIB=1 -DBOOST_SYSTEM_DYN_LINK=1 -DNDEBUG -I"." -c -o "bin.v2/libs/system/build/gcc-4.9.0/release/threading-multi/error_code.o" "libs/system/src/error_code.cpp" Full output is here: http://pastebin.com/fgReAxTE Looking at [1], boost/system/error_code.hpp does indeed include <boost/utility/enable_if.hpp>, and looking at [2], there is indeed no 'enable_if.hpp' in boost/utility, so I'm not sure how it's _supposed_ to work. What am I missing? Thanks, Nate [1] https://github.com/boostorg/system/blob/master/include/boost/system/error_c… [2] https://github.com/boostorg/utility/tree/master/include/boost/utility

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[Units] Heterogeneous unit for pressure per time
by Dina Goldshtein 28 Feb '15

28 Feb '15

Hi, I asked about this in StackOverflow<http://stackoverflow.com/questions/27519186/boost-heterogeneous-unit-bar-pe…> but didn't get any answers so I thought I'd try here as well. I need to create a unit which represents pressure per time, specifically Bar per Minute. I tried creating it in the same way as I created similar units before: typedef boost::units::derived_dimension<boost::units::length_base_dimension, -1, boost::units::mass_base_dimension, 1, boost::units::time_base_dimension, -3>::type pressure_roc_dimension; typedef boost::units::unit<pressure_roc_dimension, boost::units::make_system<boost::units::metric::bar_base_unit, boost::units::metric::minute_base_unit>::type> bar_per_minute_unit; BOOST_UNITS_STATIC_CONSTANT(BarPerMinute, bar_per_minute_unit::unit_type); typedef boost::units::quantity<bar_per_minute_unit, double> BarPerMinuteRoC; And then I try to use it: BarPerMinuteRoC bpm = 5.0 * BarPerMinute; But this line doesn't compile with quite a long error trail which I'm having a bit of trouble understanding fully. 1>c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(197): error C2039: 'item' : is not a member of 'boost::units::dimensionless_type' 1> c:\workspace\externals\boost_1_57_0\include\boost\units\dimensionless_type.hpp(37) : see declaration of 'boost::units::dimensionless_type' 1> c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(259) : see reference to class template instantiation 'boost::units::detail::determine_extra_equations_skip_zeros_impl<true,false>::apply<RowsBegin,1,1,3,Result>' being compiled 1> with 1> [ 1> RowsBegin=boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>,boost::units::detail::determine_extra_equations_skip_zeros_impl<false,true>::apply<boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>,1,0,3,boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>>,boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>>>::next_equations> 1> , Result=boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>>,boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>> 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(264) : see reference to class template instantiation 'boost::units::detail::determine_extra_equations<2,false>::apply<boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>,boost::units::detail::determine_extra_equations_skip_zeros_impl<false,true>::apply<boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>,1,0,3,Result>::next_equations>,3,Result>' being compiled 1> with 1> [ 1> Result=boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>>,boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>> 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(538) : see reference to class template instantiation 'boost::units::detail::determine_extra_equations<3,false>::apply<Matrix,3,Matrix>' being compiled 1> with 1> [ 1> Matrix=boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>>,boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>> 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(828) : see reference to class template instantiation 'boost::units::detail::make_square_and_invert<boost::units::list<boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<0,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::detail::make_zero_vector<0>::type>>>,boost::units::list<boost::units::list<boost::units::static_rational<-1,1>,boost::units::list<boost::units::static_rational<1,1>,boost::units::list<boost::units::static_rational<-2,1>,boost::units::detail::expand_dimensions<0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>>>,boost::units::dimensionless_type>>>' being compiled 1> c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(1032) : see reference to class template instantiation 'boost::units::detail::normalize_units<T>' being compiled 1> with 1> [ 1> T=boost::units::list<boost::units::scaled_base_unit<boost::units::si::second_base_unit,boost::units::scale<60,boost::units::static_rational<1,1>>>,boost::units::list<boost::units::metric::bar_base_unit,boost::units::dimensionless_type>> 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\detail\linear_algebra.hpp(1051) : see reference to class template instantiation 'boost::units::detail::calculate_base_unit_exponents_impl<false>::apply<T,Dimensions>' being compiled 1> with 1> [ 1> T=boost::units::list<boost::units::scaled_base_unit<boost::units::si::second_base_unit,boost::units::scale<60,boost::units::static_rational<1,1>>>,boost::units::list<boost::units::metric::bar_base_unit,boost::units::dimensionless_type>> 1> , Dimensions=BSII::Units::pressure_roc_dimension 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\heterogeneous_system.hpp(243) : see reference to class template instantiation 'boost::units::detail::calculate_base_unit_exponents<boost::units::list<boost::units::scaled_base_unit<boost::units::si::second_base_unit,boost::units::scale<60,boost::units::static_rational<1,1>>>,boost::units::list<T,boost::units::dimensionless_type>>,Dimensions>' being compiled 1> with 1> [ 1> T=boost::units::metric::bar_base_unit 1> , Dimensions=BSII::Units::pressure_roc_dimension 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\unit.hpp(92) : see reference to class template instantiation 'boost::units::detail::make_heterogeneous_system<Dim,System>' being compiled 1> with 1> [ 1> Dim=BSII::Units::pressure_roc_dimension 1> , System=boost::units::homogeneous_system<boost::units::list<boost::units::scaled_base_unit<boost::units::si::second_base_unit,boost::units::scale<60,boost::units::static_rational<1,1>>>,boost::units::list<boost::units::metric::bar_base_unit,boost::units::dimensionless_type>>> 1> ] 1> c:\workspace\externals\boost_1_57_0\include\boost\units\unit.hpp(99) : see reference to class template instantiation 'boost::units::reduce_unit<S1>' being compiled 1> with 1> [ 1> S1=BSII::Units::bar_per_minute_unit 1> ] 1> c:\workspace\foundations\sw_foundations\bsii_common\test\src\units\units_pressure_test.cpp(97) : see reference to class template instantiation 'boost::units::is_implicitly_convertible<BSII::Units::bar_per_minute_unit,Unit>' being compiled 1> with 1> [ 1> Unit=BSII::Units::bar_per_minute_unit 1> ] According to the Boost documentation a homogeneous system can only be composed of linearly independent base units. In my case, I'm trying to mix bars (which in turn "contain" seconds as the time element) with minutes. This sounds problematic to me. But on the other hand, since I don't include mass and length base units in my system it seems to me that the base is independent after all. In any case, I searched online for an example of creating such a heterogeneous unit but didn't find anything comprehensible. Also, I read in the Boost documentation that a heterogeneous unit doesn't preserve information about how it was created. Does this mean I won't be able to, for instance, multiply BarPerMinuteRoC by Minute and get Bar back? Thanks a lot! Dina This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any review use, dissemination, distribution, or duplication of this communication is strictly prohibited. If you are not the intended recipient, please contact the sender immediately by reply email and destroy all copies of the original. Thank you.

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[gsoc15] Attn: We need 2015 mentors and project ideas for Boost!
by Niall Douglas 10 Feb '15

10 Feb '15

Dear Boost community, We are now within one month of the beginning of Google Summer of Code 2015! Last year's GSoC furthered the continuing success of the Boost GSoC programme with the first ever Boost funded extension to a GSoC project (that being Boost.Hana by Louis Dionne mentored by Joel Falcou, congrats to both of them on passing an exceptionally tough selection process), and over $50,000 of Google funding brought to Boost in 2014. We also sent three representatives to last year's mentor summit, including one student whose entire expenses the Boost Steering Committee very generously covered. As part of filling in our application for 2015, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2015. There are a number of changes to how we design project ideas for students this year intended to improve the GSoC experience for both students and mentors, so please examine the ideas page which outlines those changes at https://svn.boost.org/trac/boost/wiki/SoC2015 and if you have any questions or concerns about those changes, please ask now rather than just before the GSoC deadline. If you think yourself able to mentor a student doing some work on Boost this summer, *please* consider adding a description of the proposed work item and your name to the list. Last year we acquired eight slots from Google and had to disappoint two mentors and students, we hope with the improved selection process we can get back to the ten annual slots we once had. If you want to know more about mentoring a Google Summer of Code funded student work before you nominate yourself, please feel free to ask on the main Boost developers mailing list boost(a)lists.boost.org. Thank you in advance for your time. Niall Douglas (Boost Google Summer of Code admin) Boris Schäling (Boost Google Summer of Code admin) --- Boost C++ Libraries Google Summer of Code 2014 admin https://svn.boost.org/trac/boost/wiki/SoC2014

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