October 2012 - Boost-users - lists.boost.org

[units] Missing quantity operator++, operator%
by Nathan Crookston 25 Oct '12

25 Oct '12

All, I'm in the process of switching my homegrown units system over to boost units. Some operators which I'm missing are the modulus and the pre and post increment operators. Looking through the archives I note an original review[1] which mentioned the absence of those operators. One response claimed that quantity<si::length, int> t = 5. ...; t++; was nonsensical as writing 5 m + 1, and the reviewer eventually agreed, citing possible confusion if the quantity type converted the initializer. Matthias Schabel seemed to respond favorably: 'I debated this for a while - the only problem is that there will be some value types with heterogeneous operator+ / operator- for which q + 1 is not the same type as q, but I guess that it is just OK for it to just give a compile error in those cases.' And Steven Watanabe said 'Will do.' I haven't found anything regarding the modulus operator. My question is, would a patch adding those operators be accepted? Thanks, Nate [1] http://lists.boost.org/Archives/boost/2007/03/119001.php

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Errors when linking a CXX executable to boost static libraries, using gcc4.7 and boost 1.51.0
by camille chambon 25 Oct '12

25 Oct '12

Hello, I'm trying to link a CXX executable to boost static libraries. My environment is: - Fedora 17 64bit - gcc 4.7 - boost 1.51.0 built with gcc 4.7 I then get the following errors : `.text._ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED2Ev' referenced in section `.text._ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED1Ev[_ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED1Ev]' of /home/cchambon/libs/lib/libpgma.a(Timeline.cpp.o): defined in discarded section `.text._ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED2Ev[_ZN5boost16exception_detail19error_info_injectorINS_16bad_lexical_castEED5Ev]' of /home/cchambon/libs/lib/libpgma.a(Timeline.cpp.o) `.text._ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED2Ev' referenced in section `.text._ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED1Ev[_ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED1Ev]' of /home/cchambon/libs/lib/libpgma.a(DistributionFactory.cpp.o): defined in discarded section `.text._ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED2Ev[_ZN5boost16exception_detail19error_info_injectorINS_12bad_any_castEED5Ev]' of /home/cchambon/libs/lib/libpgma.a(DistributionFactory.cpp.o) error: collect2: ld returned 1 exit status Does anyone know what these errors mean? Cheers, Camille

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Re: [Boost-users] Occasional blocking with tcp::socket::receive
by Stuart Siegel 25 Oct '12

25 Oct '12

I have read the documentation :-) My understanding is that it's blocking if there's no data left to be read and you ask it to read from the socket. In my case, the server has sent the data and it's there waiting for it to read. I've confirmed this via wireshark and, as I mentioned, the plain POSIX call to read (which is also blocking by the way) works as expected. ________________________________ From: nullable.type <nullable.type(a)gmail.com> To: boostusers(a)googlegroups.com Cc: "boost-users(a)lists.boost.org" <boost-users(a)lists.boost.org>; boost-users(a)lists.boost.org; ssiegel95(a)yahoo.com Sent: Thursday, October 25, 2012 3:34 AM Subject: Re: [Boost-users] Occasional blocking with tcp::socket::receive Hi Read the documentation: http://www.boost.org/doc/libs/1_51_0/doc/html/boost_asio/reference/basic_st… A call to boost::asio::ip::tcp::socket::receive(..) IS a blocking call. If you wannt to avoid blocking, just use the async_* functions. Cheers, Simon On Friday, October 19, 2012 3:50:11 PM UTC+2, Stuart Siegel wrote: The call to receive below will occasionally hang. All interactions are synchronous and single threaded. Things work perfectly if I use the alternative <sys/socket.h> (POSIX) implementation under the #else. Since I'm pretty new to boost::asio, I must be doing something wrong but after many hours of trying different things, I'm still stuck. Any advice would be appreciated. #if 1 namespace bas = boost::asio; remaining = X //(something typically about 5000 bytes of char data) bas::streambuf b; bas::streambuf::mutable_ buffers_type bufs = b.prepare(1024); while (remaining > 0) { size_t n = sock.receive(bufs); //<-------------this blocks every so often remaining -= n; for ( bas::buffers_iterator<bas:: streambuf::mutable_buffers_ type, char> it = bas::buffers_begin(bufs); it < (bas::buffers_begin(bufs) + n); it++ ) qba.append(*it); } #else //this works perfectly in the 250000 or so test calls I've hit it with char buf[1024]; while (remaining > 0) { n = read( sock, buf, min( sizeof(buf), remaining ) ); remaining -= n; for (int i = 0 ; i < n; i++ ) qba.append(buf); } #endif >

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Are shared_mutex's recursive?
by John M. Dlugosz 25 Oct '12

25 Oct '12

Clearly recursive acquiring of a shared (reading) lock is natural. But what about an exclusive lock? Can the owning thread acquire the write lock recursively, or even read locks recursively?

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Memory usage of adjacency_list
by Ed Linde 24 Oct '12

24 Oct '12

Hi, Is it possible to get a ballpark figure of the maximum memory required for an adjacency_list, given its settings? I need these statistics to report how much memory is being used initially when reading in a large graph and then after vertex removal operations and edge removal operations, how much reduction is got in this memory finally. Do I have to write something of my own to do this? Thanks, Ed -- View this message in context: http://boost.2283326.n4.nabble.com/Memory-usage-of-adjacency-list-tp4637051… Sent from the Boost - Users mailing list archive at Nabble.com.

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Is it possible to put a std::unique_ptr into a mulit_index container?
by Josh Quigley 24 Oct '12

24 Oct '12

Hi all, Is it possible to put a std::unique_ptr into a mulit_index container? In particular, the following fails. typedef std::pair<int, std::unique_ptr<int> > ValueT; typedef boost::multi_index_container< ValueT, boost::multi_index::indexed_by< boost::multi_index::hashed_unique< BOOST_MULTI_INDEX_MEMBER(ValueT, int, first) > > > HashMap; HashMap map; auto a = std::make_pair(5, std::unique_ptr<int>(new int(5))); map.insert(std::move(b)); // This line fails to compile (Visual Studio 2012) I'm guessing the answer is 'No' and it's because the rvalue reference overloads have not been done, but I'd like confirmation (or even better, to be told I'm wrong!). Thanks, Josh.

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[spirit] Parsing quoted string
by Giampiero Gabbiani 24 Oct '12

24 Oct '12

Hi together, I have to parse the following row: "a_token": true|false, the last comma is optional. Testing the following: bool value; test_parser(" \"orig_bool\": true,", qi::lit('"') >> *(ascii::alnum | qi::char_('_')) >> qi::lit('"') >> qi::lit(':') >> boost::spirit::qi::bool_[phx::ref(value)=_1] >> -(qi::lit(','))); it works, but with the following instead the program compile but hangs ... bool value; test_parser(" \"orig_bool\": true,", qi::lit('"') >> *(!qi::lit('"')) >> qi::lit('"') >> qi::lit(':') >> boost::spirit::qi::bool_[phx::ref(value)=_1] >> -(qi::lit(','))); the only difference is the way by means I get the content of the quoted string, actually instead of using *(ascii::alnum | qi::char_('_')) I'd like to use *(!qi::lit('"')) that - imho - should be better but it actually hangs. What/where am I actually missing/wrong? Many thanks in advance Giampiero

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Re: [Boost-users] asio: how to handle disk IO, recommendations
by Avi Bahra 24 Oct '12

24 Oct '12

> Currently I has a single threaded server based on boost ASIO. > This works correctly most of the time. > However on systems where i know that the disk's are slow. > , the server grinds to a halt, when dealing with the blocking > disk IO. > > I could not find any examples or documentation in ASIO, in > how to get round these issues. It appears that ASIO does > not provide any support for async' disk IO. > > So I assume this is handled by use of threads ? > Are there any examples of using ASIO with threaded disk IO, > since this must be very common use case ? > > Is the strand functionality appropriate for handing disk IO, > in an async' manner. > > Any recommendations/advice on this issues would be > greatly appreciated. > > Best regards, > Ta, > Avi > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > >Hi Avi, > >If your server performs short read/writ frequently and data to be transfer >to network depend on these operations, then multi-threading does not help a >lot here. I would suggest you to recheck your I/O strategies and make sure >they are optimized. e.g. buffering, cache, .. etc. If they are perfect but >performance still bother you, then consider to use memory mapped file or >libaio. > >Best, >Acer. In my case the ASIO server needs to only write to a local disk.(no reads) One write is relatively short, i.e to a log file, to record all requests, the other is to write periodically a in memory node tree. This can vary between 1-100MB. My thinking was that if I used a thread reserved for writing the node tree, it will not block the server from handling requests, on slow file systems. I will look into memory mapped files and libaio. Ta, Avi

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serialization
by Larry E. Ramey 24 Oct '12

24 Oct '12

I've got a system where class A { A(); A(const string&); virtual ~A(); }; class C : public A { C(); C(const A&, float); virtual ~C(); }; BOOST_CLASS_EXPORT( A ) BOOST_CLASS_EXPORT( C ) main() { ... const A* a = new a("stuff"); const C* c = new c(*a, 52.54390f); { ofstream ofs("dump.bin"); boost::archive::text_oarchive oa(ofs); oa<<a<<c; } ... A* a2=NULL; C* c2=NULL; try { ifstream ifs("dump.bin"); boost::archive::text_iarchive ia(ifs); ia>>a2; ia>>c2; } catch(boost::archive::archive_exception& ae) { cout<<ae.what(); } } This works just fine. If I replace A* a2=NULL; C* c2=NULL; with A* a2=NULL; A* c2=NULL; Then it throws an unregistered_class exception. If I change the iarchive to take: const A* a = new A("I'm cool"); const A* c = new C(*a,54.2f); then I can unarchive it with a pair of A*. Is this by design? Seriously? I can't save derived pointers and unarchive base pointers? Larry

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adding 'blackberry' to boost build
by Gottlob Frege 23 Oct '12

23 Oct '12

I work for RIM (ie BlackBerry), and am trying to make using boost as easy as possible to use for BB developers. So I would like to make building boost for BB as easy as possible. I would also like to make building boost work "as expected" for anyone who understands Boost.Build. It is the "as expected" part that I'm not sure of. ie should I just offer a blackberry-config.jam? should Boost.Build be changed to auot-detect the BB NDK? should blackberry be a toolset? a target-os? ...? how would you *expect* it hook into Boost.Build? (And note that I expect that developers *also* use the same boost for Windows, etc, so I don't want to replace/affect the simple build for the host machine.) - And finally, it would be nice if this was upstreamed back into boost build (if people think that makes sense), so that boost "just works" on BlackBerry. Here's what I have so far: from the command line, you run something like: b2 install --prefix=C:\boost\ --user-config=blackberry-config.jam --layout=system toolset=gcc target-os=qnxnto I'd prefer it if they didn't need to type so much. And the config file looks like basically the rest of this email: import os ; # these env vars are set by installing the BB NDK QNX_TARGET_ARCH = [ os.environ QNX_TARGET_ARCH ] ; QNX_TARGET = [ os.environ QNX_TARGET ] ; QNX_HOST = [ os.environ QNX_HOST ] ; if ! $(QNX_TARGET) || ! $(QNX_HOST) { ECHO error: ; ECHO error: BlackBerry build of Boost requires QNX_TARGET and QNX_HOST env variables. Did you run bbndk-env.bat? ; ECHO error: ; EXIT ; } if $(QNX_TARGET_ARCH) = x86 { dashVOpt = gcc_ntox86_cpp ; linkArchDir = x86 ; } else { dashVOpt = gcc_ntoarmv7le_cpp ; linkArchDir = armle-v7 ; } using qcc # Version : # C++-compile-command : $(QNX_HOST)/usr/bin/QCC -V$(dashVOpt) # Compiler options : <compileflags>"-D__QNX__" <compileflags>"-D__QNXNTO__" # Add -D__USE_ISOC99 for rounding control mechanism (boost/numeric/interval/hw_rounding.hpp) <compileflags>"-D__USE_ISOC99" <compileflags>"-I$(QNX_TARGET)/usr/include" # Prevent this from being output: "note: the mangling of 'va_list' has changed in GCC 4.4" <compileflags>"-Wno-psabi" # Add -fPIC to link without error to LibTestNativeLibTuTest.o (for statechart tests) <compileflags>"-fPIC" # Requested by BBM team <compileflags>"-fno-strict-aliasing" # Functions like sync_val_compare_and_swap and sync_fetch_and_add aren't available <compileflags>"-DBOOST_SP_NO_SYNC" <linkflags>"-L$(QNX_TARGET)/$(linkArchDir)/usr/lib -L$(QNX_TARGET)/$(linkArchDir)/lib" ; import option ; option.set keep-going : false ; ------------------------ Thanks in advance, Tony

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building universal boost binaries (MacOS)
by Nick Zavaritsky 23 Oct '12

23 Oct '12

Hi! Boost.build docs says that to build 'fat' binaries on the Mac two options exist: architecture=combined and/or address-model=32_64. The first one builds a binary with PowerPC and x86 code. The second one builds a binary with 32 and 64bit code. The doc further states that architectire= and address-model= are independent: one can use the first one alone or the second one alone or both simultaneously yielding different results. (http://www.boost.org/boost-build2/doc/html/bbv2/reference/tools.html#bbv2.r…) I would like to use address-mode=x86_64 to build x86/x86_64 fat binaries of boost libraries. Unfortunately with boost 1.51 it doesn't work this way — in order to get fat binaries one has to specify both architecture=combined and address-mode=32_64. Since we don't want power pc support we strip binaries from ppc code using lipo. This is a very suboptimal solution since we compile ppc variant anyway and that takes time. Even worse is that the modern toolchain doesn't support PowerPC hence we have to compile Boost using older toolchain. Currently address-model=32_64 works only if architecture=combined was specified as well (tried with Xcode 4.5 and 3.2.5). Is this really a bug in Boost.build? If that is by design what is the method to build boost fat binaries with modern toolchain lacking ppc support?

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Re: [Boost-users] [EXTERNAL] Re: [MPI] missing symbols using serialization's static library design
by Robert Ramey 23 Oct '12

23 Oct '12

"Barrett, Brian W" <bwbarre(a)sandia.gov> wrote in message news:<69A29AB53D57F54D81061A9E4E45B8FD239CC111(a)EXMB01.srn.sandia.gov>... > On 10/17/12 1:00 PM, "Robert Ramey" <ramey(a)rrsd.com> wrote: > > >Barrett, Brian W wrote: > >> > Unfortunately, I'm barely competent in using Boost.MPI and > Boost.Serialization. I'm definitely not in a position to be able to apply > a patch. > > What I'm getting from your responses and the general silence elsewhere is > that the right answer is to deal with the incompatibilities between > versions of Boost and explicitly instantiate all the internal MPI > archivers and hope for the best. It's a little painful, but I think we > can do that. Well, your organization could contract with me to address this for you. I've done special work for several companies which use the serialization library. This work has been contributed to boost and become part of the distributed package. So a) The organization gets what it needs for a reasonable cost. b) Any generally useful enhancements get included in the library So it helps everyone all around. Thanks in advance for considering this. Robert Ramey > > Thanks, > > Brian > > -- > Brian W. Barrett > Scalable System Software Group > Sandia National Laboratories

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[system] symbol visibility and GCC vs. Clang
by James Walker 23 Oct '12

23 Oct '12

When trying to link a bunch of libraries on OS X, I got this linker warning: ld: warning: direct access in boost::system::system_error::~system_error() to global weak symbol vtable for boost::system::system_error means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings. As far as I can tell, everything is compiled using the flags -fvisibility=hidden -fvisibility-inlines-hidden. I'm wondering whether the problem is that some of the libraries were built using gcc and some were built using Clang. In boost/system/system_error.hpp, the declaration of boost::system::system_error is decorated with BOOST_SYMBOL_VISIBLE. In boost/config/compiler/gcc.hpp, BOOST_SYMBOL_VISIBLE is defined to be __attribute__((visibility("default"))), whereas boost/config/compiler/clang.hpp does not define BOOST_SYMBOL_VISIBLE. -- James W. Walker, Innoventive Software LLC <http://www.frameforge3d.com/>

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Re: [Boost-users] Interesting article on stack-based TMP
by Thorsten Ottosen 23 Oct '12

23 Oct '12

On 23-10-2012 15:05, Larry Evans wrote: > On 10/22/12 07:26, Giovanni Piero Deretta wrote: > [snip] >> Now, to make this thread on-topic: is anybody working on a C++11 >> rewrite of Boost.MPL? >> > Anyone attempting such a rewrite and planning to use the > variadic template features might want to start from: > > http://svn.boost.org/svn/boost/sandbox/variadic_templates/boost/mpl/ > > However, using variadic templates may cause a slowdown in the > compile times. IIRC, a variadic template version of proto was > developed but was abandoned in favor of using: > > http://www.boost.org/doc/libs/1_51_0/libs/preprocessor/doc/index.html > > because of large compile times. Hm. This is really sad if variadic templates can't be used for the thing they were created for. Is this an inherent problem for large-scale use of variadic templates? -Thorsten

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asio: how to handle disk IO, recommendations
by Avi Bahra 23 Oct '12

23 Oct '12

Currently I has a single threaded server based on boost ASIO. This works correctly most of the time. However on systems where i know that the disk's are slow. , the server grinds to a halt, when dealing with the blocking disk IO. I could not find any examples or documentation in ASIO, in how to get round these issues. It appears that ASIO does not provide any support for async' disk IO. So I assume this is handled by use of threads ? Are there any examples of using ASIO with threaded disk IO, since this must be very common use case ? Is the strand functionality appropriate for handing disk IO, in an async' manner. Any recommendations/advice on this issues would be greatly appreciated. Best regards, Ta, Avi

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Boost install creates no boost library files
by niallm 22 Oct '12

22 Oct '12

Hi guys, I'm running OS X 10.8.2 and I'm trying to install boost. I'm using Enthought python. So I've unpacked the tar file boost_1_51_0.tar.bz2 into usr/local. Then in the resulting directory boost_1_51_0, I do the following commands: $ ./bootstrap.sh --with-python=2.7 --with-python-root=../../Library/Frameworks/EPD64.framework /Versions/Current/bin/python then: $ ./b2 link=shared --with-python --with-math (I only need the python and math parts). This returns: he Boost C++ Libraries were successfully built! The following directory should be added to compiler include paths: /usr/local/boost_1_51_0 The following directory should be added to linker library paths: /usr/local/boost_1_51_0/stage/lib Then I did: $ sudo ./b2 --prefix=usr/local link=shared --with-python --with-math install This returns: common.mkdir usr common.mkdir usr/local common.mkdir usr/local/include common.mkdir usr/local/include/boost Followed by lots of lines starting 'common.copy...' and finished with '...updated 9752 targets...'. However when I check in usr/local/include there is no boost directory, and there are no boost libraries in usr/local/lib Thanks in advance -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-install-creates-no-boost-library-f… Sent from the Boost - Users mailing list archive at Nabble.com.

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[graph] Extending bgl_named_params
by Philipp Moeller 22 Oct '12

22 Oct '12

Hi, I maintain a library that introduces its own graph properties for domain specific algorithms and provides it's own implementation of bgl_named_parameters by essentially mimicking bgl_named_parameters one-to-one. With the refactoring in 1.51 that implementation broke and I had to add another implementation of named parameters which essentially looks like this: enum my_property_t { my_property }; template <typename T, typename Tag, typename Base = boost::no_property> struct foo_bgl_named_params : boost::bgl_named_params<T, Tag, Base> { typedef boost::bgl_named_params<T, Tag, Base> base; typedef foo_bgl_named_params self; foo_bgl_named_params(T v = T()) : base(v) {} foo_bgl_named_params(T v, const Base& b) : base(v, b) {} template <typename PMap> foo_bgl_named_params<PMap, my_property_t, self> my_property_map(const PMap& p) const { typedef foo_bgl_named_params<PMap, my_property_t, self> Params; return Params(p, *this); } }; // the respective free functions... template <typename PMap> foo_bgl_named_params<PMap, my_property_t, self> my_property_map(const Pmap& p) const { typedef foo_bgl_named_params<PMap, my_property_t, self> Params; return Params(p); } // partial specialization for lookup_named_param_def namespace boost { template <typename T, typename Tag, typename Base, typename Def> struct lookup_named_param_def<Tag, foo_bgl_named_params<T, Tag, Base>, Def> { typedef T type; static const type& get(const bgl_named_params<T, Tag, Base>& p, const Def&) { return p.m_value; } }; template <typename Tag1, typename T, typename Tag, typename Base, typename Def> struct lookup_named_param_def<Tag1, foo_bgl_named_params<T, Tag, Base>, Def> { typedef typename lookup_named_param_def<Tag1, Base, Def>::type type; static const type& get(const bgl_named_params<T, Tag, Base>& p, const Def& def) { return lookup_named_param_def<Tag1, Base, Def>::get(p.m_base, def); } }; } // boost This is brittle because it the type returned by the inherited functions is not the same and chaining will not work if one of those functions is called first, e.g. all custom properties have to be chained together first. >From the documentation it is not really obvious to me if other libraries are even supposed to provide their own properties and how/if they actually should be able to extend the named parameters API. Is that simply not an intended feature of the BGL or can that be done differently? Cheers, Philipp

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Linking issue with Boost 1.44 and GCC 4.6
by Joseph Sulewski 21 Oct '12

21 Oct '12

Hi, I'm having a very strange compilation issue with Boost. I've used boost in other C++ projects in the past and have had no issues. I'm writing a program to compile against Hypertable which relies on the boost 1.44 version of the library. I'm writing this on Intel Linux and compiling with GCC 4.6.3 Here is my linker command. I removed the .o's from my application to make it simpler to read: g++ -L/opt/hypertable/current/lib -L/home/l3/development/libraries/boost_1_44_0/stage/lib -pthread -o "AppLogger" MYDOT-O-FILES.o -lboost_system -lboost_iostreams -lboost_filesystem -lboost_program_options -lboost_thread -lsigar-x86-linux -lz -lHypertable -lHyperspace -lHyperTools -lHyperComm -lHyperCommon As you can see I'm including a number of boost libraries but I'm getting a lot of very strange errors. For example, opt/hypertable/current/lib/libHypertable.a(Client.cc.o): In function `Hypertable::Client::Client(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int)': Client.cc:(.text+0x26a5): undefined reference to `boost::program_options::variables_map::variables_map()' >From what I can see the precompiled library from Hypertable is not finding the functions in the boost library. Here is another I get Client.cc:(.text+0x26a5): undefined reference to `boost::program_options::variables_map::variables_map()' /opt/hypertable/current/lib/libHypertable.a(Client.cc.o): In function `Hypertable::Client::Client(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int)': I get a bunch of these: HqlInterpreter.cc:(.text._ZN5boost9call_onceIPFvvEEEvRNS_9once_flagET_[void boost::call_once<void (*)()>(boost::once_flag&, void (*)())]+0x151): undefined reference to `boost::detail::once_epoch_cv' There are many many more linker errors but I didn't want to clog up the system with all the errors. Any ideas would be greatly appreciated Thanks

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[proto] transform with calling templates
by Felipe Magno de Almeida 21 Oct '12

21 Oct '12

Hello, I had the following transform and function object: struct bind_functions_transform : proto::when < proto::terminal<binding::placeholder::method_value<proto::_,proto::_> > , bind_method_call(proto::_value, proto::_data, proto::_state)> > struct bind_method_call : proto::callable { template <typename T> struct result { typedef typename boost::function_types::parameter_types<T>::type parameter_types; typedef typename boost::mpl::next <typename boost::remove_reference <typename boost::mpl::at_c<parameter_types, 2u>::type>::type>::type type; }; template <typename Sig, typename F, std::size_t I, std::size_t N> boost::mpl::size_t<I+1> operator()(binding::placeholder::method_value<Sig, F>const& method , boost::fusion::vector<Class&, environment, binding::virtual_table<N>&>& data , boost::mpl::size_t<I> v) const { ... } }; So, I needed one more compile-time information which would be equal to all calls and transforms, so I made my transform into a template and also bind_method_call as follows: template <typename T> struct bind_functions_transform : proto::when < proto::terminal<binding::placeholder::method_value<proto::_,proto::_> > , bind_method_call<T>(proto::_value, proto::_data, proto::_state)> > template <typename T> struct bind_method_call : proto::callable [...] And then I received the following error: ../boost_1_50_0/boost/proto/transform/detail/preprocessed/construct_funop.hpp:24:33: error: no matching function for call to ‘jvb::binding::bind_method_call<hello_world>::bind_method_call(const jvb::binding::placeholder::method_value<void(), void (hello_world::*)()>&, boost::fusion::vector<jvb::class_&, jvb::environment, jvb::binding::virtual_table<1ul>&, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_>&, const mpl_::size_t<0ul>&)’ I've remembered the workaround for msvc with proto::call. Because it seemed that the transform was actually trying to construct instead of calling bind_method_call, so I changed to: template <typename PeerClass> struct bind_functions_transform : proto::when < proto::terminal<binding::placeholder::method_value<proto::_,proto::_> > , proto::call<bind_method_call<PeerClass>(proto::_value, proto::_data, proto::_state)> > And it worked. Well, my question is: is this a known limitation? I didn't find it in proto documentation. I'm using GCC 4.7.1 and x86_64 with Linux Regards, -- Felipe Magno de Almeida

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Boost python, unique_ptr and abstract class
by Maxim Yegorushkin 19 Oct '12

19 Oct '12

I am using boost::python to expose a C++ API into Python. Here is what I am trying to do: #include <boost/python.hpp> #include <memory> struct Subscriber { virtual ~Subscriber() = 0; static std::unique_ptr<Subscriber> create(); }; template<class T> inline T* get_pointer(std::unique_ptr<T> const& p) { return p.get(); } BOOST_PYTHON_MODULE(subscriber) { // Expose the class. boost::python::class_< Subscriber , std::unique_ptr<Subscriber> , boost::noncopyable >("Subscriber"); // Expose its factory function. bp::def("createSubscriber", Subscriber::create); } boost::python::class_<> constructor invocation spits out errors (full compiler log attached): /usr/local/ots/boost-1.51.0/include/boost/python/converter/as_to_python_function.hpp:40:75: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = Subscriber; _Dp = std::default_delete<Subscriber>; std::unique_ptr<_Tp, _Dp> = std::unique_ptr<Subscriber>]’ /usr/local/ots/boost-1.51.0/include/boost/python/object/pointer_holder.hpp:194:14: error: cannot allocate an object of abstract type ‘Subscriber’ How do I make boost::python friendly to std::unique_ptr<> and how do I wrap an abstract class please? -- Maxim

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Occasional blocking with tcp::socket::receive
by Stuart Siegel 19 Oct '12

19 Oct '12

The call to receive below will occasionally hang. All interactions are synchronous and single threaded. Things work perfectly if I use the alternative <sys/socket.h> (POSIX) implementation under the #else. Since I'm pretty new to boost::asio, I must be doing something wrong but after many hours of trying different things, I'm still stuck. Any advice would be appreciated. #if 1 namespace bas = boost::asio; remaining = X //(something typically about 5000 bytes of char data) bas::streambuf b; bas::streambuf::mutable_buffers_type bufs = b.prepare(1024); while (remaining > 0) { size_t n = sock.receive(bufs); //<-------------this blocks every so often remaining -= n; for ( bas::buffers_iterator<bas::streambuf::mutable_buffers_type, char> it = bas::buffers_begin(bufs); it < (bas::buffers_begin(bufs) + n); it++ ) qba.append(*it); } #else //this works perfectly in the 250000 or so test calls I've hit it with char buf[1024]; while (remaining > 0) { n = read( sock, buf, min( sizeof(buf), remaining ) ); remaining -= n; for (int i = 0 ; i < n; i++ ) qba.append(buf); } #endif

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[Boost.Functional.OverloadedFunction][C++03] Number of overloads in boost::overload_function<...>
by Felipe Magno de Almeida 19 Oct '12

19 Oct '12

Hello, Is there a way to know how many overloads are there in a overloaded_function without resorting to preprocessor metaprogramming in C++03? It doesn't seem to be a MPL sequence, for example. Regards, -- Felipe Magno de Almeida

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boost solution for transforming stl algorithms on proxy iterators?
by Oswin Krause 19 Oct '12

19 Oct '12

Hi, I often have problems which look a bit like this: //example code, only for problem statement //std::vector<bool> chosen only because it is no container :). If this is too silly for you, //think about a matrix interpreted as range of row-vectors. std::vector<bool> myContainer;//does only have proxy iterators. std::vector<double> myDistances; //stores for every element in myContainer a distance //now i want to to sort the elements of both ranges in place //as if they were in a hypothetic range std::vector<std::pair<bool, double> > //and sort them by the second part: boost::sort(make_key_value_range(myContainer,myDistances));//bam, not allowed I omited the definition of make_key_value_range but it should be clear that this returns a proxy range with writable iterators and reference type similar to std::pair<std::vector<bool>::reference,double&> for which swap is overloaded to do the right thing. This is not allowed by the standard as boost::sort calls std::sort which in turn requires random_access_iterators - and they disallow proxy references. This issue is AFAIK resolved with C++11 but some of us still need to support C++03 - and I am really annoyed by this problem. The thing is: this will compile on most compilers. One could just lie about the iterator category, saying it is a random_access_iterator and even VC would be happy with it. However it could just break randomly on a new compiler without warning or has severe performance issus (for example gcc works, but completely ignores my nicely defined swap and instead does a triangle copy :-( ). So how can one resolve this issue? I have the problem, that i need to do this in-place, since copying would result in std::bad_alloc almost surely. Also the above single line of code just looks that nice, that i just want to have it this way. So, how do you resolve this issue? is there maybe some boost library capable of getting this done? e.g. boost.betterSTL? :-). Greetings, Oswin

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Using Adaptable Generator concept with generate_n and boost smart pointers
by Marco Craveiro 18 Oct '12

18 Oct '12

Hi boosters, I'm trying to create a class that models the concept of adaptable generator [1]. The idea is that it generates pointers to test data objects which I'd like to then put inside of smart pointers such as shared_ptr or scoped_ptr (or even std::shared_ptr) via generate_n, etc. This is a (non-compilable) example of my intentions: #include <algorithm> #include <iostream> #include <memory> #include <vector> #include <iterator> struct base { int i; }; struct derived : public base { int z; }; struct generator { typedef base result_type; result_type* operator()() { return new derived(); } }; int main(void) { std::vector<std::shared_ptr<base> > z; std::generate_n(std::back_inserter(z), 5, generator()); return 0; } The std::shared_ptr is incidental; it could have been boost::shared_ptr, etc - its up to client code to decide. I get this to work fine when result_type is say boost::shared_ptr<base> but what I really like is for it to be a raw pointer; is there some boost magic (or standard C++ 11 magic) I can apply to convert it to the value_type of the container I'm trying to generate? Many thanks for your time, Marco -- So young, and already so unknown -- Pauli blog: http://mcraveiro.blogspot.com [1] http://www.sgi.com/tech/stl/AdaptableGenerator.html

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Generically connecting a signal to a member function
by Chris Stankevitz 18 Oct '12

18 Oct '12

Hello, I wrote a function called "Connect" which generically connects a signal to a member function. The pseudo-code for this function is: void Connect(Signal, MemberFunction, pClass) { Signal.connect(Signal::slot_type(MemberFunction, pClass)); } Problem: I had to create "overloads" for different number of signal arguments. This was somewhat expected and we see it in boost with things like boost::bind. What I did not expect was that each of my overloads had to have a different name. This is because all overloads have the same function signature: one signal, one member function, one class pointer. Question: Is there a way to write a generic "Connect" that handles signals of different number of arguments? If overloading is involved, can it be done like bind such that all overloads have the same name? Below is my solution that exhibits the "problem" I described above. Thank you for your help, Chris === #include <boost/bind.hpp> #include <boost/signals2.hpp> #include <iostream> //------------------------------------- // Connect0 // // Generically connect a member // function to a signal producing zero // arguments. //------------------------------------- template < class TASignal, class TAMemberFunction, class TAClass> void Connect0( TASignal& Signal, TAMemberFunction MemberFunction, TAClass* pClass) { typedef typename TASignal::slot_type TDSlot; TDSlot Slot(MemberFunction, pClass); Signal.connect(Slot); } //------------------------------------- // Connect0 // // Generically connect a member // function to a signal producing one // arguments. //------------------------------------- template < class TASignal, class TAMemberFunction, class TAClass> void Connect1( TASignal& Signal, TAMemberFunction MemberFunction, TAClass* pClass) { typedef typename TASignal::slot_type TDSlot; TDSlot Slot(MemberFunction, pClass, _1); Signal.connect(Slot); } //------------------------------------- // Connect2 // // Generically connect a member // function to a signal producing two // arguments. //------------------------------------- template < class TASignal, class TAMemberFunction, class TAClass> void Connect2( TASignal& Signal, TAMemberFunction MemberFunction, TAClass* pClass) { typedef typename TASignal::slot_type TDSlot; TDSlot Slot(MemberFunction, pClass, _1, _2); Signal.connect(Slot); } //------------------------------------- //------------------------------------- struct TCClass { void f0() {} void f1(int) {} void f2(int, int) {} }; //------------------------------------- //------------------------------------- int main() { boost::signals2::signal<void()> Signal0; boost::signals2::signal<void(int)> Signal1; boost::signals2::signal<void(int, int)> Signal2; TCClass Class; Connect0(Signal0, &TCClass::f0, &Class); Connect1(Signal1, &TCClass::f1, &Class); Connect2(Signal2, &TCClass::f2, &Class); Signal0(); Signal1(1); Signal2(2, 2); return 0; }

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