February 2013 - Boost-users

[Preprocessor] Comma in sequence element
by Adam Badura 12 Feb '13

12 Feb '13

I have following code: #include <boost/preprocessor/seq/enum.hpp> #include <boost/preprocessor/seq/transform.hpp> template< int I, int J > struct Base { }; #define SEQ ( 1 ) ( 2 ) ( 3 ) ( 4 ) #define OP( s, data, elem ) Base< elem, elem > struct Derived : BOOST_PP_SEQ_ENUM( BOOST_PP_SEQ_TRANSFORM( OP, nil, SEQ ) ) { }; The Derived has bases classes generated from a sequence (SEQ). The bases classes themselves are instantiations of Base template type. I expected the code to be preprocessed into something like (just the important part): struct Derived : Base< 1, 1 >, Base< 2, 2 >, Base< 3, 3 >, Base< 4, 4 > { }; but instead it is preprocessed into: struct Derived : Base< 1, Base< 2, Base< 3, Base< 4 { }; This obviously is caused by Base being template with to parameters and thus having a comma. Adding parenthesis around Base in OP solves the issue by generating expected code fully. But it still does not compile because parenthesis are not allowed in that place (base classes list). Is there any other workaround? How to deal with it?

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udp::socket::socket() vs udp::socket::open()
by Chris Stankevitz 11 Feb '13

11 Feb '13

Hello, The UDP async server example opens the udp socket like so: a) udp::socket::socket(io_service, udp::endpoint(udp::v4(), 13)) Boost's comment regarding this invocation: * This constructor creates a datagram socket and automatically opens it bound * to the specified endpoint on the local machine. The protocol used is the * protocol associated with the given endpoint. Please consider the udp::socket constructor that takes only an io_service: b) explicit basic_datagram_socket(boost::asio::io_service& io_service) Commented as: * This constructor creates a datagram socket without opening it. The open() * function must be called before data can be sent or received on the socket. And finally, udp::socket::open: (c) void open(const protocol_type & protocol = protocol_type()); Please note that (a) takes an endpoint while (c) takes a protocol. === Question: How can I effectively call (a) using the two-part invocation (b) then (c)? Answer: 1) Just call udp::socket::open(endpoint(udp::v4(), 13)); 2) This is impossible because (a) takes a endpoint while (c) wants a protocol 3) Why would you want to do that you moron? 4) Why don't you write your own udp::socket::open that takes an endpoint if you are so smart? Try giving back to the community instead of just taking. You are a leech and not worthy of reading this mailing list let alone posting to it. 5) none of the above Note: (1) fails with error: no matching function for call to 'boost::asio::basic_datagram_socket<boost::asio::ip::udp>::open(boost::asio::ip::udp::endpoint)' Thank you, Chris

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Extracting subgrapshs
by dheeraj_kumar 11 Feb '13

11 Feb '13

Hello, It will very helpfull if anybody provide some sample code for Extracting list of subgraps's from a Graph. Regards, Dheeraj -- View this message in context: http://boost.2283326.n4.nabble.com/Extracting-subgrapshs-tp4642616.html Sent from the Boost - Users mailing list archive at Nabble.com.

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modifying default compiler path
by Mahmood Naderan 11 Feb '13

11 Feb '13

Hi I have an old version of boost 1.33.1. I want to build it with a custom gcc binary whih is in a path other than default. I could not find the page on the web so I paste the first part of the gcc-tools.jam form tools/build/v1/gcc-tools.jam. # singleton variables... set-as-singleton GCC_ROOT_DIRECTORY GCC_BIN_DIRECTORY GCC_INCLUDE_DIRECTORY GCC_STDLIB_DIRECTORY ; flags gcc GCC_BIN_DIRECTORY : $(GCC_BIN_DIRECTORY) ; flags gcc GCC_INCLUDE_DIRECTORY : $(GCC_INCLUDE_DIRECTORY) ; flags gcc GCC_STDLIB_DIRECTORY : $(GCC_STDLIB_DIRECTORY) ; GCC_BIN_DIRECTORY ?= $(GCC_ROOT_DIRECTORY)$(SLASH)bin ; GCC_BIN_DIRECTORY ?= "" ; # Don't clobber tool names if GCC_ROOT_DIRECTORY not set GCC_STDLIB_DIRECTORY ?= $(GCC_ROOT_DIRECTORY)$(SLASH)lib ; # Make sure this gets set "on" the target flags gcc GCC_BIN_DIR : $(GCC_BIN_DIRECTORY) ; In this part I can modify the default gcc/g++ to my own using the variables which are defined in the comment section. However I don't know How to do that. For example, I write GCC_BIN_DIRECTORY=/opt/gcc-4.1.2/installed But that gives me this error: rule GCC_ROOT_DIRECTORY=/opt/gcc-4.1.2/installed unknown in module So how can I do that? Regards, Mahmood

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[Thread] 1.53 fails to compile working code
by Szymon Gatner 10 Feb '13

10 Feb '13

Hello, following minimal code compiles fine with 1.52 and BOOST_THREAD_VERSION defined to 3 but gives compilation error with 1.53 release (Visual Studio 2008 SP1, Win 7): #include <boost/move/move.hpp> #include <boost/thread/future.hpp> class Dummy { public: Dummy& operator=(BOOST_RV_REF(Dummy) other); Dummy& operator=(BOOST_COPY_ASSIGN_REF(Dummy) other); BOOST_COPYABLE_AND_MOVABLE(Dummy); }; Dummy createDummy(); int main() { boost::future<Dummy> df = boost::async(&createDummy); } Error message: 1>------ Build started: Project: boost_153_test, Configuration: Debug Win32 ------ 1>Compiling... 1>main.cpp 1>c:\devel\boost_1_53_0\boost\thread\future.hpp(661) : error C2665: 'boost::detail::future_traits<T>::init' : none of the 2 overloads could convert all the argument types 1> with 1> [ 1> T=Dummy 1> ] 1> c:\devel\boost_1_53_0\boost\thread\future.hpp(525): could be 'void boost::detail::future_traits<T>::init(boost::scoped_ptr<T> &,Dummy &)' 1> with 1> [ 1> T=Dummy 1> ] 1> c:\devel\boost_1_53_0\boost\thread\future.hpp(530): or 'void boost::detail::future_traits<T>::init(boost::scoped_ptr<T> &,boost::rv<T> &)' 1> with 1> [ 1> T=Dummy 1> ] 1> while trying to match the argument list '(boost::scoped_ptr<T>, const Dummy)' 1> with 1> [ 1> T=Dummy 1> ] 1> c:\devel\boost_1_53_0\boost\thread\future.hpp(655) : while compiling class template member function 'void boost::detail::future_object<T>::set_value_at_thread_exit(const T &)' 1> with 1> [ 1> T=Dummy 1> ] 1> c:\devel\boost_1_53_0\boost\thread\future.hpp(1542) : see reference to class template instantiation 'boost::detail::future_object<T>' being compiled 1> with 1> [ 1> T=Dummy 1> ] 1> c:\devel\boost_1_53_0\boost\thread\future.hpp(1415) : see reference to class template instantiation 'boost::shared_future<R>' being compiled 1> with 1> [ 1> R=Dummy 1> ] 1> c:\devel\boost_1_53_0\boost\thread\future.hpp(1413) : while compiling class template member function 'boost::future<R>::future(boost::rv<T> &)' 1> with 1> [ 1> R=Dummy, 1> T=boost::future<Dummy> 1> ] 1> c:\users\bravo\documents\visual studio 2008\projects\boost_153_test\boost_153_test\main.cpp(19) : see reference to class template instantiation 'boost::future<R>' being compiled 1> with 1> [ 1> R=Dummy 1> ] 1>Build log was saved at "file://c:\Users\Bravo\Documents\Visual Studio 2008\Projects\boost_153_test\boost_153_test\Debug\BuildLog.htm" 1>boost_153_test - 1 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Btw: why BOOST_THREAD_VERSION is still 2 when documentation says it is 4.0.0 as of boost 1.53? Regards, Szymon Gatner -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

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[Interprocess] WIN32 define case unaccessible ?
by Antoine Pédron 10 Feb '13

10 Feb '13

Hello, I'm using Boost.Interprocess in order to get a single portable source code between Windows and Linux using Mutexes and Shared Memory. Documentation says that, for Windows, the API default behaviour is emulation with mapped files, which is the case (:D). Though, having a look at interprocess' headers, i encountrered this case : from D:\Libraries\boost\boost_1_51\boost\interprocess\sync\named_mutex.hpp : ____________________________________________________________________________ #if defined(BOOST_INTERPROCESS_NAMED_MUTEX_USES_POSIX_SEMAPHORES) #include <boost/interprocess/sync/posix/named_mutex.hpp> #define BOOST_INTERPROCESS_USE_POSIX_SEMAPHORES #elif !defined(BOOST_INTERPROCESS_FORCE_GENERIC_EMULATION) && defined (BOOST_INTERPROCESS_WINDOWS) #include <boost/interprocess/sync/windows/named_mutex.hpp> #define BOOST_INTERPROCESS_USE_WINDOWS #else #include <boost/interprocess/sync/shm/named_mutex.hpp> #endif ____________________________________________________________________________ A case where BOOST_INTERPROCESS_FORCE_GENERIC_EMULATION is not defined and BOOST_INTERPROCESS_WINDOWS is, meaning that i can use Windows standard API. My problem is that i want to use this case and i wonder how to reach it. The former file includes boost/interprocess/detail/workaround.hpp where both symbols are defined : ____________________________________________________________________________ #if defined(_WIN32) || defined(__WIN32__) || defined(WIN32) #define BOOST_INTERPROCESS_WINDOWS #define BOOST_INTERPROCESS_FORCE_GENERIC_EMULATION #define BOOST_INTERPROCESS_HAS_KERNEL_BOOTTIME ____________________________________________________________________________ and i can't see an #undef anywhere to get into the case i want. Thanks in advance, Antoine

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Testing whether result_of<F(U)> is a valid expression
by oswin krause 08 Feb '13

08 Feb '13

Hi, Is it possible to evaluate, whether a certain argument type given to a functor will lead to a valid expression with the result_of template? i am trying to achieve the following, maybe there is a better way to do it: template<class T, class F> Container< typename boost::result_of<F(T)>::type > transform( Container<T> c, F f, std::disable_if<valid_expression<F(Block<T>) > >::type* dummy = 0 ){ //slow default implementation Container<T> res(c.size()); std::transform(c.begin(),c.end(),res.begin(),f): return res; } //blocked implmentation of transform template<class T, class F> Container< typename boost::result_of<F(T)>::type > transform( Container<T>, F functor, std::enable_if<valid_expression<F(Block<T>) > >::type* dummy = 0 ){ //functor supports fast implementation Container<T> res(c.size()); std::transform(c.blocks().begin(),c.blocks().end(),res.blocks().begin(),functor): return res; } the question is, how valid_expression<F(Block<T>) > could be implemented and right now the only mechanism which get's close to what i want would be checking result_of<F(Block<T>)> is valid. Greetings, Oswin

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Re: [Boost-users] How do you compile Boost C++ code in Ubuntu?
by Giovanni 08 Feb '13

08 Feb '13

Greetings All, Thank you so much, Mr. Maddock. I was able to compile my program successfully and resolve my linking errors with your help. Also, thank you very much, Mr. Loskot! I appreciate all the precious time that you have spent to help me out. Have an awesome weekend! Regards On Fri, Feb 8, 2013 at 8:20 AM, John Maddock <boost.regex(a)virgin.net> wrote: > It is a quirk of GCC that the libraries used by a source file must appear > *after* the source file. Nothing to do with Boost really... > > John. On Fri, Feb 8, 2013 at 9:45 AM, Mateusz Loskot <mateusz(a)loskot.net> wrote: > On 8 February 2013 16:03, Giovanni <giovanni.ong(a)comsoc.org> wrote: >> I followed your instructions to link the libraries, with the >> "-lboost_filesystem -lboost_system" sequence of linking the >> aforementioned Boost C++ libraries. >> >> However, I cannot resolve the linking error. I have included a >> snippet from my Terminal session below. > > No idea what's wrong really and have no time to investigate it. > But, I've done quick test on Ubuntu 10.04 using Boost 1.40 > installed from its packages and small sample from this book > http://en.highscore.de/cpp/boost/errorhandling.html > and it worked for me: > > Here is my console log: > > mloskot@vb-ubuntu104-x64:~/tmp$ /usr/bin/lsb_release -d > Description: Ubuntu 10.04.4 LTS > > mloskot@vb-ubuntu104-x64:~/tmp$ cat bsystem.cpp > #include <boost/system/error_code.hpp> > #include <iostream> > #include <string> > > class application_category : > public boost::system::error_category > { > public: > const char *name() const { return "application"; } > std::string message(int ev) const { return "error message"; } > }; > > application_category cat; > > int main() > { > boost::system::error_code ec(14, cat); > std::cout << ec.value() << std::endl; > std::cout << ec.category().name() << std::endl; > } > > mloskot@vb-ubuntu104-x64:~/tmp$ g++ -L/usr/lib -lboost_system bsystem.cpp > mloskot@vb-ubuntu104-x64:~/tmp$ ./a.out > 14 > application > > mloskot@vb-ubuntu104-x64:~/tmp$ ldd ./a.out |grep boost > libboost_system.so.1.40.0 => /usr/lib/libboost_system.so.1.40.0 > (0x00007f2df87b6000) > > > Perhaps something has changed in later versions. > I have no time to dig it deeper, sorry. > > Best regards,

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Re: [Boost-users] How do you compile Boost C++ code in Ubuntu?
by Giovanni 08 Feb '13

08 Feb '13

Greetings, I realized that when I installed certain packages from the Ubuntu Software Center, I had broken some dependencies. That may have caused the problem. Now, I have reinstalled Boost C++. See the following for a snippet from the Terminal session that indicates the availability of the previously missing files. Go Bears >ls -al | grep libboost_system -rw-r--r-- 1 root root 48666 Jan 2 2012 libboost_system.a lrwxrwxrwx 1 root root 17 Jan 2 2012 libboost_system-mt.a -> libboost_system.a lrwxrwxrwx 1 root root 25 Jan 2 2012 libboost_system-mt.so -> libboost_system.so.1.46.1 lrwxrwxrwx 1 root root 25 Jan 2 2012 libboost_system.so -> libboost_system.so.1.46.1 -rw-r--r-- 1 root root 14568 Jan 2 2012 libboost_system.so.1.46.1 Go Bears > Go Bears >make all g++ -L/usr/lib -lboost_system get_sys_info.cpp /tmp/cckONUUl.o: In function `__static_initialization_and_destruction_0(int, int)': get_sys_info.cpp:(.text+0x13f): undefined reference to `boost::system::generic_category()' get_sys_info.cpp:(.text+0x14b): undefined reference to `boost::system::generic_category()' get_sys_info.cpp:(.text+0x157): undefined reference to `boost::system::system_category()' /tmp/cckONUUl.o: In function `boost::filesystem3::path::codecvt()': get_sys_info.cpp:(.text._ZN5boost11filesystem34path7codecvtEv[boost::filesystem3::path::codecvt()]+0x5): undefined reference to `boost::filesystem3::path::wchar_t_codecvt_facet()' collect2: ld returned 1 exit status make: *** [all] Error 1 Go Bears > So, I am back to square one with the "undefined reference" compilation error. Can you please kindly suggest how can I resolve this problem? Thank you. Regards On Thu, Feb 7, 2013 at 8:33 AM, Mateusz Loskot <mateusz(a)loskot.net> wrote: > On 7 February 2013 15:21, Giovanni <giovanni.ong(a)comsoc.org> wrote: >> >> I had set the shell variable $LD_LIBRARY_PATH to: >> /usr/lib/libboost_system.so. It was originally empty. I used the >> "echo" command to reflect the path that I had set it to. > > I tried to make a point not about how you did set the variable, > but about the fact it has incorrect value. > Let me copy it once again: > > "LD_LIBRARY_PATH, which is a colon-separated list of directories" [1] > > [1] http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html > > And you may learn from that what the LD_LIBRARY_PATH is meant to be. > >> I had installed it with Ubuntu Software Center. >> Here is a snippet of: /usr/lib >> [...] >> -rw-r--r-- 1 root root 14568 Jan 2 2012 libboost_system.so.1.46.1 >> -rw-r--r-- 1 root root 14568 Jan 5 2012 libboost_system.so.1.48.0 > > You seem to be missing libboost_system.so library or symlink named > libboost_system.so with one of the two as a target. > It may look the installation is broken. > >> When I followed your instructions to install it (again), I couldn't. >> Here is the transcript from the Terminal. >> Go Bears >sudo apt-get install libboost-system-dev >> [sudo] password for arvind: >> Reading package lists... Done >> Building dependency tree >> Reading state information... Done >> Some packages could not be installed. This may mean that you have >> requested an impossible situation or if you are using the unstable >> distribution that some required packages have not yet been created >> or been moved out of Incoming. >> The following information may help to resolve the situation: >> >> The following packages have unmet dependencies: >> libboost-system-dev : Depends: libboost-system1.46-dev but it is not >> going to be installed >> E: Unable to correct problems, you have held broken packages. > > Clearly, something is broken with installation of boost packages in your system. > You should seek for help from Ubuntu folks, it's unrelated to Boost. >

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[python] how to call python's built-in type() function
by Eric Niebler 08 Feb '13

08 Feb '13

In C++, I have a boost::python::object that is wrapping ... something. I'd like to find out what. If I were in python land, I'd call the built-in 'type' function on it. What do I do in C++? Thanks in advance, -- Eric Niebler Boost.org

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