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Using boost with explicit template instance
by ranadheer p 11 Oct '11

11 Oct '11

We have built a C++ library using Boost and when we try to integrate the library in a binary we are having problem in linking because of “--instances=explicit” option used for building the binary. The problem is, when we use --instances=explicit option (of Sun CC compiler) it expects us to instantiate the templates explicitly. As Boost internally uses templates when we use Boost with this option the linker is throwing “Undefined symbol” errors - which is expected as we are not instantiating the templates used in Boost explicitly. Though I understand why the linker is throwing the error here, it looks tricky to instantiate all boost templates explicitly in the code. So, want to check if there any solution/workaround to use Boost with “-instances=explicit” option of Sun CC compiler. Any help is much appreciated. We can reproduce the problem with simple sample code as - #include<iostream> #include<boost/lexical_cast.hpp> intmain() { std::cout<<boost::lexical_cast<int>(“8”)<<std::endl; } With “--instances=explicit” option Undefined first referenced symbol in file __type_0 boost::detail::lexical_cast<unsigned,std::string,false,char>(__type_0,__type_3*,unsigned) lexical.o ld:fatal:Symbolreferencing errors.Nooutput written to a.outWithout “--instances=explicit” option this works fine

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ptr_vector<> and vector<shared_ptr<>> compatibility
by Jan Vogelgesang 11 Oct '11

11 Oct '11

Hi, today i had to switch from ptr_vector<MyType> to vector<shared_ptr<MyType> > (needed weak_ptr's to these elements somewhere else). Unfortunately the interfaces of these two containers are quite different when it comes to element access, e.g., ptr_vector<MyType> returns a reference to MyType vs. vector<shared_ptr<MyType> >operator[] returns a reference to a shared_ptr<MyType>. In my case i had a hard time replacing countless occurrences of "BOOST_FOREACH(MyType& e, getMyTypeContainerFromSomewhere())". I'am wondering whats your opinion about a shared_ptr_vector<> that will comply to a ptr_sequence_adapter, using shared_ptr<> to store the elements, and including the possibility to get access to the shared_ptr<> ? Is there any reason why such a container is a bad idea (and thus not already part of the library)? greetings Jan

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[MPL] return type
by Istvan Buki 11 Oct '11

11 Oct '11

Dear Boost experts, I'm trying to find a solution to the following problem. I'm iterating over an MPL sequence and once I found the appropriate type in the sequence I call a static function that returns a pointer to a newly created object that I need to return to the caller of the ModelDispatcher::parse member function with its exact type. In other words I need to propagate the exact type of the object created somewhere in a recursive chain of function calls back to the original caller. Unfortunately I can't figure out how to specify the return type of this recursive function. Every type in the sequence has the following form: struct sequence_item { typedef the_real_type type ; static the_real_type *parse( const QDomElement & ) ; } ; The code for iterating over the sequence is the following: template < typename It, typename End > ?? *dispatchM( const QDomElement &, mpl::true_ /* endofvec */ ) { return 0 ; } template < typename It, typename End > ?? *dispatchM( const QDomElement &element, mpl::false_ ) { typedef typename mpl::deref< It >::type MapEntry ; if ( element.tagName() == MapEntry::first::name() ) { // return type is MapEntry::second::type return MapEntry::second::parse( element ) ; } else { typedef typename mpl::next< It >::type Next ; return dispatchM< Next, End >( element, typename boost::is_same< Next, End >::type() ) ; } } template < typename ModelMap > struct ModelDispatcher { static ?? *parse( const QDomElement &element ) { mpl::false_ f ; return dispatchM< typename mpl::begin< ModelMap >::type, typename mpl::end< ModelMap >::type >( element, f ) ; } } ; Thanks a lot for your help. Istvan

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[Graph] troubles with pointer properties
by Paolo Fogliaroni 11 Oct '11

11 Oct '11

Hello everyone, my first post here, so I hope not to miss some mailing list rule. I'm experiencing some problems in using graph internal properties. I have to generate a graph from a database and I need to differentiate nodes in my graph, namely I will have 2 different node categories, say cat1_node and cat2_node. Each category should have its own property attached. Ex: say N1 is a cat1_node and N2 is a cat2_node. I want N1 to have a "name" (string) property while N2 a "length" (int) property and both have a "label" (string) property. To achieve this I though I could use inheritance in the following manner: //FATHER PROPERTY CLASS class generic_vertex_property{ public: generic_vertex_property(){type = 0;} int type; std::string label; }; //SON PROPERTY CLASS class cat1_property: public generic_vertex_property{ public: std::string name; }; //SON PROPERTY CLASS class cat2_property: public generic_vertex_property{ public: int length; }; In this way, I though, I can define my graph something like: typedef adjacency_list< vecS, vecS, directedS, property<vertex_p_t, generic_vertex_property*> > Graph; and add new vertices like: cat1_property *v1 = new cat1_property(); cat2_property *v2 = new cat2_property(); v1->label = "v1_label"; v1->name = "v1_name"; v2->label = "v2_label"; v2->length = 10; add_vertex(VertexProperty(v1),G); add_vertex(VertexProperty(v2),G); This actually compiles and runs without errors. The problem comes when I try to access the verteces through a property_map, like: vertex_p_map_t vertex_p_map = get(vertex_p, G); //where vertex_p_map_t and vertex_p have been define before Indeed from such get function I have objects of type generic_vertex_property, thus, when trying to access a property of the sone classes I got this compile error: error: ‘class generic_vertex_property’ has no member named ‘name’ I hope I was clear enough, if necessary I can also send the full code. In the meanwhile here are my questions: Is it possible to do what I want to do? Is there a way to get a property map with the "original" object types (as inserted)? Do you have some good websites with practical examples, code snippets and so on about BGL? Last question comes as, in my opinion, the reference manual is quite complete, but 1) lot of examples are not compiling ( look like they have not been updated to the last boost version) 2) examples are usually very basic and it is very hard to get the general rules behind it. hope someone can help me out with this. bests, Paolo

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bind with weak_ptr
by Christopher Pisz 11 Oct '11

11 Oct '11

I see many posts when I google this problem. I wonder, since most of them are dated 1.35 and previous, if there was ever a solution to this problem? I think this fellow says it best when he posted, "My problem is, that when i bind member functions, if i specify the instance of the class as a shared_ptr, then i get memory leaks because the binding's shared_ptr to the instance keeps it alive, and it potentially produces cyclic references that in the current model, would be complicated to break. And of course, if i use raw pointers to the binding instances, then i'll get a crash if the instance has been destroyed and i try to execute the binding function. So what i would need, is to use bind with weak pointers, and just do nothing if locking it fails." http://www.gamedev.net/topic/494089-help-boostbind-and-shared-pointers/ I've almost went to just using raw pointers and letting the program crash if the instance to which the member bound no longer exists. I hate to do that.

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math tools roots
by Matwey V. Kornilov 11 Oct '11

11 Oct '11

Hi all, I believe that there is a bug in eps_tolerance implementation. At line 34 of toms748_solve.hpp one can see: return (fabs(a - b) / (std::min)(fabs(a), fabs(b))) <= eps; When both a and b equal zero this condition is evaluated to a false instead of a true. Left hand of condition is NaN and the right one is a floating- point number hence the result is false. Well obviously, a user wants to see true here because the relative length of interval in this case tend to zero.

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Re: [Boost-users] What about achieving strong erection?
by Daniel Bradburn 11 Oct '11

11 Oct '11

..Stop difficulty sleeping and a loss of appetite! http://fuhes.the-best-web-sites.com/com.friend.php?tonid_hotmail=83v3

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testing command-line interface using Boost.Test
by Olaf Meeuwissen 11 Oct '11

11 Oct '11

Dear all, I've been using Boost.Test with Test First and TTD approaches to library development and am one happy hacker. All tests are integrated with our continuous integration setup so we get test reports with every build. Now I'm starting on a few command-line utilities and would like to use Boost.Test to do the same. I have something simple going now with a test fixture to help with redirecting standard input, output and error and running commands in a way that the test runner does not hang when a command-line invocation returns a failure status. The gist of my tests would be as follows when testing the GNU coreutils `true` and `false` utilities BOOST_AUTO_TEST_CASE (test_false) { BOOST_CHECK_EQUAL (EXIT_FAILURE, my_system ("false")); } BOOST_AUTO_TEST_CASE (test_true) { BOOST_CHECK_EQUAL (EXIT_SUCCESS, my_system ("true")); } where my_system() basically does explicitly what system() would do for you. See [1] for an implementation of my_system(). When using system() instead of my_system(), the test runner fails the first test incorrectly(!) and hangs. It starts but never finishes the second test. Using my_system() the first tests still incorrectly fails but now at least the second tests completes and succeeds as expected. The first test produces unknown location(0): fatal error in "test_false": child has exited; pid: 19788; uid: 1000; exit value: 1 and I assume it never gets to the comparison that BOOST_CHECK_EQUAL() is supposed to do. Any suggestions on how to get this to work? Maybe even alternative approaches to testing command-line interfaces? [1] http://www.gnu.org/software/libc/manual/html_node/Process-Creation-Example.… Thanks in advance, -- Olaf Meeuwissen, LPIC-2 FLOSS Engineer -- AVASYS CORPORATION FSF Associate Member #1962 Help support software freedom http://www.fsf.org/jf?referrer=1962

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Boost.Thread and thread-priority
by Andrej van der Zee 11 Oct '11

11 Oct '11

Hi, I have a question about thread priority in combination with Boost.Thread. I implemented a pool of threads that reads data-pkts from a work-queue in user-space. The main-thread receives data-packets from the kernel, copies them into user-space and places them in this data-queue. It is important that the kernel buffers do not overflow and therefor I thought raising the priority of the main-thread is a good idea. My question is would this *really* help? And how do I change priority with Boost.Thread? Cheers, Andrej

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Problems installing boost 1.47.0
by Allan Nielsen 10 Oct '11

10 Oct '11

Hi I'm trying to install boost 1.47 in a single threaded edition but it does not seems to work. Here is what I tried: ./bootstrap.sh --without-icu --without-libraries=graph_parallel,mpi,python ./b2 threading=single --layout=system --prefix=/usr/local Here is the error I got on the second command: Building the Boost C++ Libraries. Performing configuration checks - has_icu builds : yes - ../config//has_gcc_visibility builds : yes - ../config//has_long_double_support builds : yes /storage/src/boost_1_47_0/tools/build/v2/build/virtual-target.jam:1079: in virtual-target.register-actual-name from module virtual-target error: Duplicate name of actual target: <pstage/lib>libboost_system.so.1.47.0 error: previous virtual target { common%common.copy-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.link.dll-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.compile.c++-error_code.o.OBJ { error_code.cpp.CPP } } } } error: created from ./stage-proper error: another virtual target { common%common.copy-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.link.dll-libboost_system.so.1.47.0.SHARED_LIB { gcc%gcc.compile.c++-error_code.o.OBJ { error_code.cpp.CPP } } } } error: created from ./stage-proper error: added properties: <threading>single <warnings>on error: removed properties: <threading>multi <warnings>all /storage/src/boost_1_47_0/tools/build/v2/build/virtual-target.jam:490: in actualize-no-scanner from module object(file-target)@2784 /storage/src/boost_1_47_0/tools/build/v2/build/virtual-target.jam:135: in object(file-target)(a)2784.actualize from module object(file-target)@2784 /storage/src/boost_1_47_0/tools/build/v2/build-system.jam:749: in load from module build-system /storage/src/boost_1_47_0/tools/build/v2/kernel/modules.jam:283: in import from module modules /storage/src/boost_1_47_0/tools/build/v2/kernel/bootstrap.jam:142: in boost-build from module /storage/src/boost_1_47_0/boost-build.jam:17: in module scope from module Is there anything I can do to fix this locally ?? Best regards Allan W. Nielsen

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