February 2016 - Boost-users

Boost.Context stack growing inwards
by Thomas Ziegenhagen 29 Feb '16

29 Feb '16

Hi there, I get regular crashes when using Boost.Context after just a few calls to make_fcontext(). I built a minimal example as follows: ---- #include <iostream> #include <vector> #include <boost/context/all.hpp> struct Context { boost::context::fcontext_t c_outside, c_inside; }; Context gContext = { nullptr, nullptr }; void DoIt( intptr_t /*pt*/) { uint8_t test[64]; memset( test, 0xaf, sizeof( test)); std::cout << "DoIt(), Point 1" << std::endl; boost::context::jump_fcontext( &gContext.c_inside, gContext.c_outside, 0, true); std::cout << "DoIt(), Point 2" << std::endl; boost::context::jump_fcontext( &gContext.c_inside, gContext.c_outside, 0, true); std::cout << "DoIt(), Point 3" << std::endl; boost::context::jump_fcontext( &gContext.c_inside, gContext.c_outside, 0, true); } int main() { const size_t StackSize = 16384; std::vector<uint8_t> stack( StackSize, 0xf1); gContext.c_inside = boost::context::make_fcontext( stack.data() + 256, stack.size() - 512, DoIt); std::cout << "main(), Point 1" << std::endl; boost::context::jump_fcontext( &gContext.c_outside, gContext.c_inside, 0, true); std::cout << "main(), Point 2" << std::endl; boost::context::jump_fcontext( &gContext.c_outside, gContext.c_inside, 0, true); std::cout << "main(), Point 3" << std::endl; boost::context::jump_fcontext( &gContext.c_outside, gContext.c_inside, 0, true); std::cout << "main(), Point 4" << std::endl; return 0; } ------ This notable thing is that I provide a stack with additional 256 bytes of safety borders. And it turns out: the provided memory is overwritten way beyond the beginning. The actual designated area is not touched at all, but instead the area before the beginning is overwritten. The only thing I found in the documentation is this: "sp Member: Pointer to the beginning of the stack (depending of the architecture the stack grows downwards or upwards)." which hints that on some system the stack might grow to negative addresses. But up to now I thought that boost.context knows which direction is correct, and adjusts the given pointer accordingly. But apparently it doesn't. Or the environment underwent a drastic change. Here it is Windows 10 64bit, Visual Studio 2015. For readers remembering my last mails: I have verified this also with an "classic" boost build using this command line: b2.exe -a --reconfigure variant=debug,release link=static runtime-link=static --with-context So I'm pretty sure it's not a build issue. Question: is this a bug? Probably not, I'm surely not the first to use Boost.Context, so I wonder what the correct way is to handle this issue. So what do I do about this? Thanks in advance Bye, Thomas

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Boost.Spirit Karma: how to store generator?
by Matwey V. Kornilov 28 Feb '16

28 Feb '16

Hello, After reading Karma tutorial, I still don't understand whether there a way to store generator except auto my_generator = ... I would like to generate text representation for many similar objects and I think that it is worth to use single generate object and pass it to generate_delimited() by const reference. Are there such things like qi::rule<> and qi::grammar for Karma?

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[ sorting_view ] -do not sort arrays, sort iterators instead
by Boris Kats 27 Feb '16

27 Feb '16

The sorting procedure is one of the most usable routine in programming.And all sorting template functions have the same signature:template< class RandomIt, class Compare >void sort( RandomIt first, RandomIt last, Compare comp );with conditions: the type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.It is clear that in the sorting process a lot of records are moving in the memory andwhen these records have a big size, these movements, together with calling constructors, can be very expensive.Solution.The proposed template function sorting_view is free of that problem - the sorting procedureis working (and moving) on tiny objects - iterators. As result of that procedure,the initial array of records is remaining intact; however provided std::vector<int> viewallows indirect access to the sorted array. On many occasions user does not need the sortedarray at all and he/she has a luxury to iterate through sorted and unsorted arrays simultaneously.In case of real needs of sorted array, it can be obtained via other template function apply_view with exactly 2*N movements of the records, where N is the size of initial array.For getting sorted view of arrays of user's defined records the appropriate Compare template function should be supplied.Happy sorting, Boris Kats.

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Help: Errors compiling SESHAT project
by C. Ichongiri 26 Feb '16

26 Feb '16

Hey there, I've been at this for days now and can't seem to find anything to help with this: I got the project at https://github.com/falvaro/seshat and followed the instructions exactly as-is: - Got the *Boost* headers - Have got *g++ *compiler ( versions 5.2, 4.9, 4.7, 4.5, 4.3) and my default *clang++* *- Makefile *is present *P.S.* I'm on *OS X Mavericks*; Used *MacPorts* to install all above gcc versions *except *5.2, which was manually done following this tutorial: https://solarianprogrammer.com/2015/05/01/compiling-gcc-5-mac-os-x/#comment… However, when I attempt to compile it, I get the following errors (attached in the Textfile below). A screenshot image also attached shows the filesystem and path I am working with, from where the error file was created. Honestly, I'm at my wits end now, especially with my being new to C++. ANY helpful insight into this would be MOST APPRECIATED. Much thanks in advance, chiich.

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Build Boost.Context with Visual Studio
by Thomas Ziegenhagen 26 Feb '16

26 Feb '16

Hi there, I'm building the required portions of Boost myself, along with all my other projects. It turned out that even the smallest compiler setting changes lead to strange crashes, some of which only occured on 5% of the client's systems, so I will not use externally built boost libraries anymore. So now I'm building the parts of boost which I require, which works fine so far. The trouble starts when I tried to use Boost.Context. It also contains ASM code, which I now need to build in Visual Studio 2015. VS2015 does not have builtin Asm support, for x64 it never had. So I'm invoking the Microsoft assembler as a custom build step. Command line is as follows: ml64 /Fo path/to/obj/file.obj /c path/to/source/jump_x86_64_ms_pe_masm.asm Documentation is as scarce as usual, but I figured from the filename that jump_x86_64_ms_pe_masm.asm is the correct file for Microsoft Visual Studio, x64. But assembling failed, and to add insult to injury, the error messages are lost somewhere in the output piping process. The complete output reads like this: ------ 1>------ Erstellen gestartet: Projekt: boost, Konfiguration: Debug x64 ------ 1> Microsoft (R) Macro Assembler (x64) Version 14.00.23506.0 1> Copyright (C) Microsoft Corporation. All rights reserved. 1> 1> Assembling: C:\Projekte\DeadPlanet\SourceExt\boost\context\asm\jump_x86_64_ms_pe_masm.asm 1> C:\Projekte\DeadPlanet\SourceExt\boost\context\asm\jump_x86_64_ms_pe_masm.asm(80)ied size 1>: error A2008 : syntax error : FRAME 1> C:\Projekte\DeadPlanet\SourceExt\boost\context\asm\jump_x86_64_ms_pe_masm.asm(81)ied size 1>CUSTOMBUILD : warning A4020: directive ignored outside a procedure 1> C:\Projekte\DeadPlanet\SourceExt\boost\context\asm\jump_x86_64_ms_pe_masm.asm(215 1>CUSTOMBUILD : fatal error A1010: unmatched block nesting : jump_fcontext ------ Please note that the actual error messages are overwritten by the filename - I can only guess at what buffer magic happens there, but I'm pretty sure it's not intended. But that's just a funny anecdote. My actual question is: how do I build Boost.Context in Visual Studio? Is there maybe some way to see the effective command line when building using Boost.Jam? Is this even the right ASM file for x86_64, Visual Studio? Thanks in advance! Bye, Thomas

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Spherical Bessel function (nu, x as real) implementation
by campagne 26 Feb '16

26 Feb '16

Dear developpers, 1) Does you use this reference to compute Spherical Bessel Functions for real argument? Accurate recursive generation of spherical Bessel and Neumann functions for a large range of indices E. Gillman <http://scitation.aip.org/content/contributor/AU0510272>^1 and H. R. Fiebig <http://scitation.aip.org/search?value1=H.+R.+Fiebig&option1=author&option91…>Comput. Phys. 2, 62(1988); http://dx.doi.org/10.1063/1.168296 2) is there a way to speed up the computation of j_nu(x) if one wants 10 digits accuracy for instance? Best regards J.E

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[ASIO] Resolver question
by Davies, John 25 Feb '16

25 Feb '16

I have some pretty simple UPD code. (It has to be simple, I'm new at ASIO) boost::asio::ip::udp::resolver::query query(boost::asio::ip::udp::v4(), addr, port); m_receiverEndpoint = *m_resolver.resolve(query); If my address is 192.168.1.112 everything works If my address is 192.168.001.112 it doesn't work and throws an exception about not finding the host. It's not a big deal, but it sure took me a long time to track down. Is there some sort of Boost magic I can do to convert the bad address into a good address? Thanks, John ________________________________ The information contained in this message may be confidential and legally protected under applicable law. The message is intended solely for the addressee(s). If you are not the intended recipient, you are hereby notified that any use, forwarding, dissemination, or reproduction of this message is strictly prohibited and may be unlawful. If you are not the intended recipient, please contact the sender by return e-mail and destroy all copies of the original message.

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Boost Thread Compile Issue
by Len Za 25 Feb '16

25 Feb '16

When simply including into C++ project and attempting to compile causes the following compile error: Environment: - Visual Studio 2010 Pro (Project Configuration: DLL project) - boost v1.60.0 C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(99): error C2146: syntax error : missing ';' before identifier 'curr' C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(81) : while compiling class template member function 'boost::posix_time::ptime boost::date_time::microsec_clock<time_type>::create_time(boost::date_time::microsec_clock<time_type>::time_converter)' with [ time_type=boost::posix_time::ptime ] C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/thread/thread_time.hpp(22) : see reference to class template instantiation 'boost::date_time::microsec_clock<time_type>' being compiled with [ time_type=boost::posix_time::ptime ] C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(99): error C2065: 'curr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(100): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(100): error C2065: 'curr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(101): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(101): error C2227: left of '->tm_year' must point to class/struct/union/generic type type is ''unknown-type'' C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(102): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(102): error C2227: left of '->tm_mon' must point to class/struct/union/generic type type is ''unknown-type'' C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(103): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(103): error C2227: left of '->tm_mday' must point to class/struct/union/generic type type is ''unknown-type'' C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(111): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(111): error C2227: left of '->tm_hour' must point to class/struct/union/generic type type is ''unknown-type'' C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(112): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(112): error C2227: left of '->tm_min' must point to class/struct/union/generic type type is ''unknown-type'' C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(113): error C2065: 'curr_ptr' : undeclared identifier C:\src\SDK\Boost\boost_1_60_0\boost_1_60_0\boost/date_time/microsec_time_clock.hpp(113): error C2227: left of '->tm_sec' must point to class/struct/union/generic type type is ''unknown-type''

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(no subject)
by Виктория Доможакова 24 Feb '16

24 Feb '16

Hello. I have template class. I want to serialize it. But I don't know how. template <class T> class AverDayVisTask : public DrawTask, public AverDayVisMathTask <T> { public: // some functions private: friend class boost::serialization::access; //! boost::serialize template <class Archive> void serialize(Archive& ar, const unsigned int /*version*/) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(DrawTask); ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(AverDayVisMathTask<T>); //<----- error } }; // class AverDayVisTask BOOST_CLASS_VERSION(AverDayVisTask<SphericalModel>, 1); BOOST_CLASS_VERSION(AverDayVisTask<SphericalNutModel>, 1); BOOST_CLASS_VERSION(AverDayVisTask<WGS84Model>, 1); BOOST_CLASS_IMPLEMENTATION(AverDayVisTask<SphericalModel>, boost::serialization::object_class_info); BOOST_CLASS_IMPLEMENTATION(AverDayVisTask<SphericalNutModel>, boost::serialization::object_class_info); BOOST_CLASS_IMPLEMENTATION(AverDayVisTask<WGS84Model>, boost::serialization::object_class_info); How fix my problem? -- Виктория Доможакова

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[graph] abort algorithm execution from a visitor
by Frank Tetzel 23 Feb '16

23 Feb '16

Hi all, i played around with the bfs example calculating distances to all vertices. Now i just want to calculate the distance between two vertices, so i want to stop when the target vertex is visited. If i understood the visitor concept correctly it's not really possible to change the behaviour of the algorithm from a visitor. Does anybody know of any workaround to do early exit? Do i have to implement a new algorithm for this? In a different thread on this list Paolo Bolzoni wrote that he aborts in a custom visitor by throwing an exception. Is this the only way? I'm using bfs here and not dijkstra because i have uniform edge weights. Btw, if someone could fix the documentation that would be really nice: http://www.boost.org/doc/libs/1_60_0/libs/graph/doc/bfs_visitor.html The code snippet there did not work for me. I had to wrap make_bfs_visitor() in visitor() like it is done in examples/bfs.cpp too. Regards, Frank

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