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

Scheduled Outage : Web sites / Trac
by Michael Caisse 17 Feb '17

17 Feb '17

We are planning the final move of services from IU this week. Expect service outages for all web sites including Trac on 17-February-2017 between 16:00 UTC - 00:00 UTC. The mail lists will continue to operate during this time; however, all other sub-domains for boost.org will be affected. Sync'ing bandwidth with IU has been low recently and has caused us to increase the outage window. We will notify these lists when services are available again. Thank you for your patience during the move. -- Michael Caisse Ciere Consulting ciere.com

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type() Segmentation Fault
by Samuel Jiménez Gil 16 Feb '17

16 Feb '17

Hi, I've got a very strange segmentation error that stems from calling type() method in any class. Surprisingly, this only occurs in another compilation that I have where I link with other gnu libraries. In both cases I am compiling with -std=c++11 and cygwin32. Is anybody aware of type() method conflicting with other libraries? Many thanks. Best regards. -- Samuel Jiménez Gil. Ph.D. Student Real-Time Systems Group, Department of Computer Science University of York Heslington York, UK YO10 5GH Email disclaimer: http://www.york.ac.uk/docs/disclaimer/email.htm

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[test] bitwise checks for non-integer types
by Norbert Wenzel 14 Feb '17

14 Feb '17

I was just surprised that BOOST_CHECK_BITWISE_EQUAL does not simply take two memory ranges and compares them bitwise, but requires integers (or types that support bit shifting). I wanted to compare two floats after binary deserialization and wanted to make sure all bits had been placed correctly, before doing value comparison. What I came up with now is a reinterpret_cast to uint8_t* and then using bitwise comparison byte for byte. I would have expected the test framework to do exactly that internally. Is comparing anything besides integers bitwise considered a bad practice or is there another reason for this limitation of BITWISE_EQUAL? If there is a rationale could that be documented at [0], since the documentation currently only speaks of unconstrained "values". thanks, Norbert [0] http://www.boost.org/doc/libs/1_63_0/libs/test/doc/html/boost_test/utf_refe…

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[serialization]: Possible to not escape double quotes
by Forumer 4umer 14 Feb '17

14 Feb '17

Hello, I am using boost serialization to save some parameteres into an xml file but this xml file is parsed through gettext tools to generate translations. The macro used for generations is _("") so my xml should look like this: <ProcedureSchema> <procedures class_id="4" tracking_level="0" version="0"> <count>1</count> <item_version>0</item_version> <item> <Name>_("Full procedure")</Name> </item> </procedures> </ProcedureSchema> The problem is boost serialization escapes double quotes with " : <Name>_("Full procedure")</Name> Would it be possible to not escape double quotes ? or at least provide a parameter that allows it ?

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Boost.Log and reinitializing text file backend on I/O errors
by Tero Saarni 13 Feb '17

13 Feb '17

Hi, I'm using text file sink to log into a file on NFS filesystem. I would like to make logging more robust when it comes to unreliability of NFS. I've registered an exception handler to ignore I/O errors, but I don't know how to re-open the log file automatically so that logging would continue when the filesystem is online again. My first try was to remove and reinitialize all sinks when the exception handler is called, but this seems to cause deadlock. Is there a way to simply re-open the associated file which caused the exception? -- Tero

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[accumulator] std::chrono::duration in boost::accumulator
by georg＠schorsch-tech.de 12 Feb '17

12 Feb '17

I want to build a histogram of `std::chrono::high_resolution_clock::duration` object. For this issue i wanted to use boost::accumulators as the framework. As it did not compile in my project i teared it down and based it on a running example with `double` as a data type. My general goal on my project is to do use for everything united types. Time and all measured stuff. I would want to avoid to use `.count()` on the duration. Is there any known workaround around this? it is not dependent on the compiler as it seems. With gcc 6.3 it failes too. It compiles when i use clang++-3.9 --std=c++14 -g -O0 main.cpp But when i set the define USE_CHRONO it failes with the error: clang++-3.9 --std=c++14 -g -O0 -DUSE_CHRONO main.cpp In file included from main.cpp:7: /usr/include/boost/accumulators/statistics/density.hpp:75:15: error: no matching constructor for initialization of 'array_type' (aka 'vector<std::chrono::duration<unsigned long, std::ratio<1, 1000000000> > >') , samples_in_bin(num_bins + 2, 0.) ^ ~~~~~~~~~~~~~~~~ and here is my teared down example. I used this site as a base and exhanged double to data_t. http://programmingexamples.net/wiki/CPP/Boost/Histogram #include <vector> #include <algorithm> #include <iostream> #include <chrono> #include <boost/accumulators/accumulators.hpp> #include <boost/accumulators/statistics/density.hpp> #include <boost/accumulators/statistics/stats.hpp> using namespace boost; using namespace boost::accumulators; using duration_t = std::chrono::high_resolution_clock::duration; #ifdef USE_CHRONO using data_t = duration_t; data_t construct(double d) { return std::chrono::milliseconds(0); } #else using data_t = double; data_t construct(double d) { return d; } #endif using acc = accumulator_set<data_t, features<tag::density> >; using histogram_type = iterator_range<std::vector<std::pair<data_t, data_t> >::iterator >; template <typename T> class data_filler { public: data_filler(){} T operator()() { return rand()/(T)RAND_MAX; } }; template <> class data_filler<duration_t> { public: data_filler(){} duration_t operator()() { return std::chrono::milliseconds(rand()/RAND_MAX); } }; int main(int argc, char** argv) { //create some random data std::vector<data_t> data(100); std::generate(data.begin(), data.end(), data_filler<data_t>()); int c = data.size();//cache size for histogramm. //create an accumulator acc myAccumulator( tag::density::num_bins = 20, tag::density::cache_size = 10); //fill accumulator for (int j = 0; j < c; ++j) { myAccumulator(data[j]); } auto hist = density(myAccumulator); data_t total = construct(0.0); for( int i = 0; i < hist.size(); i++ ) { // std::cout << "Bin lower bound: " << hist[i].first << ", Value: " << hist[i].second << std::endl; total += hist[i].second; } //std::cout << "Total: " << total << std::endl; //should be 1 (and it is) return 0; }

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boost::icl::contains question
by Sanchay Harneja 09 Feb '17

09 Feb '17

Hi, boost::icl::interval_map<int, boost::icl::interval_map<int, boost::icl::interval_set<int>>> larger, smaller; larger.add(make_pair(boost::icl::discrete_interval<int>::closed(102,104), boost::icl::interval_map<int, boost::icl::interval_set<int>>{ make_pair(boost::icl::discrete_interval<int>::closed(0,0), boost::icl::interval_set<int>{boost::icl::discrete_interval<int>::closed(2,4)})})); smaller.add(make_pair(boost::icl::discrete_interval<int>::closed(103,103), boost::icl::interval_map<int, boost::icl::interval_set<int>>{ make_pair(boost::icl::discrete_interval<int>::closed(0,0), boost::icl::interval_set<int>{boost::icl::discrete_interval<int>::closed(3,3)})})); cout << larger << endl; cout << smaller << endl; cout << boost::icl::contains(larger, smaller) << endl; cout << ((smaller & larger) == smaller) << endl; As given above, I'm trying to check if smaller is subset of larger. But I get following output: {([102,104]->{([0,0]->{[2,4]})})} {([103,103]->{([0,0]->{[3,3]})})} 0 1 Any reason why boost::icl::contains(larger, smaller) doesn't work but ((smaller & larger) == smaller) works? Thanks.

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Thread safe full duplex sockets
by Christi258 08 Feb '17

08 Feb '17

This question has been asked many times, but I'm still not satisfied with the answers. I want to use a socket in full duplex: 1. asynchronously: with async_read, async_write (multiple threads running io_service.run()) 2. synchronously: with read and write in two distinct threads I am pretty sure that 1. is thread safe using strands. But I can find no information about 2. Please refere to any official documents of boost. -- View this message in context: http://boost.2283326.n4.nabble.com/Thread-safe-full-duplex-sockets-tp469155… Sent from the Boost - Users mailing list archive at Nabble.com.

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[serialization] Object reference tracking on instances bug?
by Robert P 07 Feb '17

07 Feb '17

In my serialize function I am exporting a class which is a template wrapper around std:vector. template <typename E> class MyArray { public: vector<E> array; ... template <typename Archive> void MyArray::serialize(Archive & ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(array); } } When I add unique class instance variables to this array and then serialize it to XML... ... MyArray<Color> colorsArray; Color a; a.name = "one"; colorsArray.add(a); Color b; b.name = "two"; colorsArray.add(b); ... template <typename Archive> void MyColorsObject::serialize(Archive & ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(colorsArray); } Sometimes the XML comes out using object_id_reference instead of the unique values, and this then gets improperly unserialized with incorrect values, i.e. both colors will have "one" as the name. I was able to disable object tracking and it works now, but I don't think it should be doing object reference tracking on instance variables. Is it because of the template wrapper around vector?

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[gsoc17] Attn: We need 2017 mentors and project ideas for Boost!
by Niall Douglas 07 Feb '17

07 Feb '17

Dear Boost community, We are now a few weeks from the beginning of Google Summer of Code 2017! Last year we had the big surprise of being rejected by Google as an org, the second time ever, on the basis that Google felt we needed a year off. Thanks to the quick actions of the Boost Steering Committee and IMC Financial Markets we managed to put together a "Boost Summer of Code" so the students with projects in progress would not be left stranded. Despite a fair few teething problems, I think that worked out okay. As part of filling in our application for 2017, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2017 in order to be approved as an organisation this year. Therefore a lengthy page of awesome project ideas at https://svn.boost.org/trac/boost/wiki/SoC2017 before *February 9th* would be an enormous help to getting us approved again this year and bringing to Boost another US$35,000 of Google funding. 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. The year before last we had more slots awarded to us by Google than we had good combinations of student and mentor, so we had to return slots which I believe has not happened here at Boost GSoC in at least a decade. That means that your project ideas have a better chance than ever of receiving funding if you can find a good student, and that is best done by getting project ideas floated *early*. 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 or via gsoc-admin(a)boost.org. Thank you in advance for your time.

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[MultiIndex] Prevent automatic re-indexing after "modify"?
by Deniz Bahadir 06 Feb '17

06 Feb '17

Hi guys, Hi Joaquín, I have a question concerning the automatic re-indexing of Boost.MultiIndex indexes. Is it somehow possible to modify a member of the element-type that is used as key for (another) index without triggering automatic re-indexing? (Of course, I want to be able to trigger manual re-indexing later.) Or is it at least possible to adjust the code so that this can be achieved? To understand my question, here is my use-case and why I need it. I have a boost::multi_index_container with multiple indexes (one hashed_unique and four hashed_non_unique). I am accessing a range of elements through a hashed_non_unique index 'A'. Then I am iterating through these elements and want to modify the value of a member 'M' of each element. However, that member is used when calculating the key for another hashed_non_unique index 'B'. Therefore, I must use the "modify" function of index 'A'. The problem is now that it takes forever to modify the entire range. (We are talking about 100 thousands if not millions of entries that need to be modified.) Probably because re-indexing is triggered after each call to "modify". However, in my case it should be perfectly fine to postpone the re-indexing after I modified the entire range, because I am not going to access any element through index 'B' until I finished modifying the entire range. As a workaround I removed index 'B' from the container and declared the element-member 'M' as mutable. This allows me to directly change the value of 'M'. The speedup is astonishing. It now finishes almost in no time. But this workaround is not really feasible as it requires reimplementing index 'B' by somehow tracking the information outside of the multi_index_container. Therefore, my question really is: Is it possible to provide an "unsafe_modify" function, which does the same as "modify" but does not trigger automatic re-indexing, and an "refresh_index" function, which (manually) triggers the re-indexing? Thanks, Deniz

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Re: [Boost-users] Boost iostreams for binary data
by Bjorn Reese 06 Feb '17

06 Feb '17

On 01/31/2017 09:25 PM, Robert Dailey wrote: > I have my own BinaryInputStream and BinaryOutputStream classes that > simply take a reference to some container that meets the requirements > of random access and contiguous internal memory. It doesn't own this > container, but rather serves as an adapter to the container to allow > stream operators to be used for streaming out data. For example, you > can stream a `std::uint32_t` to the binary stream, and it will insert > 4 elements into an internal byte vector which is just > `std::vector<std::uint8_t>`. Do they work with arrays?

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[clang-win][bjam][context] '-c' is not recognized as an internal or external command
by Mikhail Strelnikov 06 Feb '17

06 Feb '17

Hello Boost, I'd like to build Boost.Context with clang on Windows with BB. There are my files: site-config.jam: using clang-win : : "C:/Program Files/LLVM/bin/clang-cl.exe" : <compatibility>vc14 <cxxflags>-Xclang <cxxflags>-std=c++1z <cxxflags>-DBOOST_USE_WINDOWS_H <cxxflags>-DNOMINMAX <cxxflags>-DWIN32_LEAN_AND_MEAN <cxxflags>-D_HAS_AUTO_PTR_ETC=1 ; Jamroot: local BOOST_ROOT = [ modules.peek : BOOST_ROOT ] ; project main : source-location . : requirements <include>$(BOOST_ROOT) <define>BOOST_ALL_NO_LIB=1 ; use-project /boost : $(BOOST_ROOT) ; exe main : main.cpp /boost//coroutine /boost//date_time ; main.cpp int main() {} I run the command: b2.exe -d+2 toolset=clang-win address-model=64 link=static runtime-link=static release -sBOOST_ROOT=D:\path\to\boost This gives me following error: clang-win.compile.asm D:\path\to\boost\bin.v2\libs\context\build\clang-vc14-win\release\link-static\runtime-link-static\threading-multi\asm\make_x86_64_ms_pe_gas.obj -c -Zp4 -Cp -Cx -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG /W3 -Fo "D:\path\to\boost\bin.v2\libs\context\build\clang-vc14-win\release\link-static\runtime-link-static\threading-multi\asm\make_x86_64_ms_pe_gas.obj" "D:\path\to\boost\libs\context\src\asm\make_x86_64_ms_pe_gas.asm" '-c' is not recognized as an internal or external command, Am I doing something wrong? Thanks.

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[mpl] Working with map, copy and back_inserter
by ☂Josh Chia (謝任中) 05 Feb '17

05 Feb '17

I'm trying to implement a compile-time topological sort of the DAG representing a certain dependency relationship between my classes. One of the data structures I can use to implement topological sort is a map, so I'm trying to use mpl::map using mpl::size_t<> as key. The documentation doesn't define key equality for mpl::map, but I assume it's effectively std::is_same<>. If so, I think I have a problem. In the following code, the last two lines fail static_assert(). The essence of the problem is that my attempt to construct/build my keys using copy with back_inserter does not give me a mpl::vector<> of mpl::size_t<> that is_same to Count, the expected value. It does give me a sequence, and the elements have the right value and value_type but they are not is_same to the expected size_t<> types. So, if I use the elements together with the size_t<> in an mpl::map, won't they be considered to be different keys? Josh #include <type_traits> #include <boost/mpl/at.hpp> #include <boost/mpl/back_inserter.hpp> #include <boost/mpl/copy.hpp> #include <boost/mpl/equal.hpp> #include <boost/mpl/equal_to.hpp> #include <boost/mpl/range_c.hpp> #include <boost/mpl/size_t.hpp> #include <boost/mpl/vector.hpp> using namespace std; namespace mpl = boost::mpl; using Empty = typename mpl::vector<>; using Count = mpl::vector<mpl::size_t<0>, mpl::size_t<1>>; using ConstructedCount = typename mpl::copy< typename mpl::range_c<size_t, 0, 2>, mpl::back_inserter<Empty>>::type; using The0 = typename mpl::at<ConstructedCount, mpl::size_t<0>>::type; using The1 = typename mpl::at<ConstructedCount, mpl::size_t<1>>::type; static_assert(mpl::equal<Count, ConstructedCount, mpl::equal_to<mpl::_1, mpl::_2>>::value, "succeeds"); static_assert(The1::value == 1, "succeeds"); static_assert(std::is_same<typename The1::value_type, size_t>::value, "succeeds"); static_assert(std::is_same<Count, ConstructedCount>::value, "fails"); static_assert(std::is_same<The1, mpl::size_t<1>>::value, "fails");

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[mpl] at<> behaves differently for vector_c<> and vector<>
by ☂Josh Chia (謝任中) 05 Feb '17

05 Feb '17

I asked earlier in a post "[mpl] Working with map, copy and back_inserter". This is a related question. The common question is: What does compile-time equality means in MPL, particularly for map and set key equality? Does it mean std::is_same? The following code works whether USE_VECTOR_C is defined as 0 or 1 -- the last 2 lines are static_asserts that have conditions determined by USE_VECTOR_C so that they succeed, highlighting the difference in behavior between USE_VECTOR_C == 0 and USE_VECTOR_C == 1. USE_VECTOR_C == 0 is the normal case where everything is working as I expect. USE_VECTOR_C == 1 is the unexpected case where the static_asserts in the last 2 lines have conditions altered so that they succeed. Why do vector_c and vector give me different "element values"? In general, what should I be careful about when trying to use the "compile-time values" as keys to avoid the situation elucidated by the last line, where I expect two "compile-time values" to be the same but they are not, resulting in two set/map items instead of one? To clarify, I'm using boost 1.63 with gcc 6.3.1 and -std=c++14 on Arch Linux. Josh #include <type_traits> #include <boost/mpl/at.hpp> #include <boost/mpl/insert.hpp> #include <boost/mpl/set.hpp> #include <boost/mpl/size.hpp> #include <boost/mpl/size_t.hpp> #include <boost/mpl/vector.hpp> #include <boost/mpl/vector_c.hpp> using namespace std; namespace mpl = boost::mpl; #define USE_VECTOR_C 0 using Zero = mpl::size_t<0>; #if USE_VECTOR_C == 1 using Vector = mpl::vector_c<size_t, 0>; #else using Vector = mpl::vector<Zero>; #endif using ZeroElt = typename mpl::at<Vector, Zero>::type; using EmptySet = mpl::set<>; using NonEmptySet = typename mpl::insert<typename mpl::insert<EmptySet, Zero>::type, ZeroElt>::type; static_assert(ZeroElt::value == 0, ""); static_assert(is_same<ZeroElt::value_type, size_t>::value, ""); static_assert(is_same<ZeroElt, Zero>::value == !USE_VECTOR_C, ""); static_assert(mpl::size<NonEmptySet>::value == USE_VECTOR_C + 1, "");

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context library of boost: compiling for windows 32 on ubuntu 64
by Jack Kumba 04 Feb '17

04 Feb '17

Hello, I want to compile libboost_context.a for windows 32 on my ubuntu 64. for that, I specify the following in my user-config.jam file using gcc : : "i686-w64-mingw32-g++" ; and then, I run the following: b2 --with-context toolset=gcc target-os=windows variant=release link=static address-model=32 binary-format=pe architecture=x86 this gives me the following error: libs/context/src/unsupported.cpp:7:2: error: #error "platform not supported" #error "platform not supported" ^ "i686-w64-mingw32-g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -march=i686 -mthreads -m32 -DBOOST_ALL_NO_LIB=1 -DBOOST_CONTEXT_SOURCE -DBOOST_DISABLE_ASSERTS -DNDEBUG -I"." -c -o "bin.v2/libs/context/build/gcc-mingw-5.3.1/release/binary-format-pe/build-no/link-static/target-os-windows/threading-multi/unsupported.o" "libs/context/src/unsupported.cpp" ...failed gcc.compile.c++ bin.v2/libs/context/build/gcc-mingw-5.3.1/release/binary-format-pe/build-no/link-static/target-os-windows/threading-multi/unsupported.o... full message is posted here: https://thepasteb.in/p/y8hzcR93o3XO7t2 It seems like the context library of boost is not supported to compile for windows on linux? Is it the case? Thanks, Aja

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Can I config process_id to log file name in the .ini setting file using Boost.Log?
by Bruce 04 Feb '17

04 Feb '17

Hi, I am using Boost.Log to output log file and using .ini file to config it. Now I need to start the exe file from the same directory for more than two instance with different start id, something like this: >start my_app.exe 1 >start my_app.exe 2 But currently only the first instance output the log content and the second one can't get the log file because the two exe uses the same log file. So I need to tell the app to use the different log file. So I want to config the .ini file to add process_id to the output file name, but I don't know how? I want to config the ini file like this but it failed:-( FileName="./log/mylog_%ProcessID%.log" Is there a way to add precess id to the output file name? Thanks.

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Boost iostreams for binary data
by Robert Dailey 03 Feb '17

03 Feb '17

I have my own BinaryInputStream and BinaryOutputStream classes that simply take a reference to some container that meets the requirements of random access and contiguous internal memory. It doesn't own this container, but rather serves as an adapter to the container to allow stream operators to be used for streaming out data. For example, you can stream a `std::uint32_t` to the binary stream, and it will insert 4 elements into an internal byte vector which is just `std::vector<std::uint8_t>`. I did not implement these in terms of IO streams, because those seemed a bit overkill and make a lot of assumptions on the data being text-only. Also I can't stream binary data into vectors, lists, and other containers because the data simply can't be parsed. Each stream out of a binary vector must be done so with a finite count of bytes. Would it make sense to implement these objects in terms of the IOstream facilities provided by boost? I know these were designed to make defining stream classes easier, but honestly I don't have a lot of experience with them. Any feedback on this? Thanks in advance. I can provide some example code if needed.

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Mail List Migration - Update
by Michael Caisse 02 Feb '17

02 Feb '17

The Boost mail lists are now migrated to a new set of servers. This change affected all mail lists and web resources (signing up, changing passwords, moderator access, archives...) that were associated with the domain lists.boost.org . If you are having difficulties, please drop me an email. (Oh the irony) Happy coding! michael -- Michael Caisse Ciere Consulting ciere.com

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Mail Lists Migrate at 00:00 UTC Feb 3
by Michael Caisse 02 Feb '17

02 Feb '17

The following mail lists will be switched to new infrastructure at 00:00 UTC on February 3rd. There will be a small interruption while the DNS/MX records propagate. * Boost - Boost developers' mailing list * Boost-announce - Boost announce-only mailing list * Boost-bugs - Bugs reported/updated through Boost's Trac * Boost-build - Boost.Build developer's and user's list * Boost-cmake - Discussion of the CMake-based build system for Boost * Boost-commit - Boost Subversion commit messages * Boost-docs - Discussion of Boost Documentation * Boost-Interest - Moderated announcements of interest to the Boost community. * Boost-maint - Boost community maintenance mailing list * Boost-mpi - Discussion of Boost.MPI development * Boost-test - Test list for the boost mailing lists * Boost-Testing - Running Boost regression tests * Boost-users - Boost Users mailing list * Geometry - Boost.Geometry library mailing list * glas - Generic Linear Algebra Software * proto - Discussions about Boost.Proto and DSEL design * threads-devel - Discussions about the boost.thread library * ublas - ublas mailing list -- Michael Caisse Ciere Consulting ciere.com

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Cross compiling context library of boost for windows 32 on a linux 64-bit machine
by Jack Kumba 01 Feb '17

01 Feb '17

Hello, Did someone succeed cross compiling context library of boost for windows 32 on a linux 64-bit machine? OR Is it even possible? I see the following error: libs/context/src/unsupported.cpp:7:2: error: #error "platform not supported" #error "platform not supported" Also, there is this ticket on this issue https://svn.boost.org/trac/boost/ticket/7262 Please advise me. Thanks, Jack

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