- Boost-users - lists.boost.org

Re: [Boost-users] enable_shared_from_this()
by John M. Dlugosz 07 Feb '13

07 Feb '13

On 2/5/2013 9:43 AM, boost-users-request-at-lists.boost.org |Boost/Allow to home| wrote: From: Dominique Devienne<ddevienne(a)gmail.com> > Thanks for any insight on this. Could very well be I'm missing > something obvious (my C++ expertise doesn't rise to Boost levels), but > so far I fail to see the drawbacks. My old smart pointers (dating back to the '90's) had full support for initializing a smart pointer from a raw pointer even if it was already known to the smart pointer system. It was one of six _essential_ features (I called it “lost and found”) and I agree there were no troubles with it. It is easy to do when the class is derived from a helper base (like enable_shared_from_this does) and furthermore it doesn't need the CRTP. I agree that an extension to the now-standard enable_self_from_this could be implemented that gives a self_from_this that may be called during the constructor or as the first way to obtain a shared_ptr, also provide for "lost and found" usage, and not behave differently for any usage that is well-formed using the standard class (that is, it would be a pure extension). When changing some existing code to use shared_ptr, I've wished something like that was available, and missed my old class in this respect. For new code, in general use a Create static member that wraps the call to the (private) constructor so you can't create anything other than a shared_ptr, and the stuff that needs the shared ptr during "construction" gets moved to the stage 2, in the body of Create. In particular, if the object registers itself with collaborators (via shared pointers) you really wanted that part _in_ the constructor. —John

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How do you compile Boost C++ code in Ubuntu?
by Giovanni 07 Feb '13

07 Feb '13

Greetings, I cannot compile my Boost C++ code. Initially, it complains of “undefined reference”. When I try to resolve this by including the library, I get the "/usr/bin/ld: cannot find -lboost_system" error. From the Terminal: Go Bears >echo $LD_LIBRARY_PATH /usr/lib/libboost_system.so Go Bears >make all g++ -L/usr/lib -lboost_system get_sys_info.cpp /usr/bin/ld: cannot find -lboost_system collect2: ld returned 1 exit status make: *** [all] Error 1 Go Bears > Do you know what stupid mistakes did I make? >From my Makefile: all: g++ -L/usr/lib -lboost_system get_sys_info.cpp ./a.out Thank you so much, and have an awesome day!

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Using property_tree as json reader/writer
by niXman 07 Feb '13

07 Feb '13

Hi, Tell me please, anybody trying to use property_tree as json reader/writer for tasks more difficult than reading configuration files? Just wondering if anyone compared the performance of property_tree and other parsers? Thanks.

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[BGL][Serialization] Reading a graph from a binary file: "vector subscript out of range error" and portability
by Nicholas Mario Wardhana 07 Feb '13

07 Feb '13

Hi all, I am trying to read a graph from a binary file. This file was previously generated by constructing a graph consisting of 1000 vertices and almost 10M edges. While vertices are properly loaded, I encountered a "vector subscript out of range error" when edges are being loaded in adj_list_serialize.hpp, line 97 (boost::tie(e,inserted) = add_edge(verts[u], verts[v], graph);). At this line, u and v are all in the order of millions, whereas I only have 1000 vertices. When I ran the program without debugging, it consumed the whole memory. I put a not-so-minimal working code at the end of my e-mail. Could somebody please point out any mistake in my code? FYI, I use Boost 1.52, Visual C++ 2010, Windows 7 64-bit. BTW, my aim is to generate save files which are fast to be read and can be read on different computers. I am aware that while this binary format can be processed fast, it is not portable. Can somebody please tell me how non-portable it is? If there are only a few things to be considered, for example architectural difference (32 vs 64-bit), it is fine as I only need to generate two files for one graph. But, if there are many of such factor, to the point that it is impossible to provide numerous save files, is there any equally fast format which is more portable? Thank you! Best regards, Nicholas Mario Wardhana //======================= CODE ===================================// #include <boost/graph/adjacency_list.hpp> #include <boost/graph/adj_list_serialize.hpp> #include <boost/archive/binary_oarchive.hpp> #include <boost/archive/binary_iarchive.hpp> #include <fstream> struct Point { Point() : x(0.0f), y(0.0f), z(0.0f) { } float x; float y; float z; }; struct Node { Point point; float maxRadius; int motionType; int label; int ID; }; struct Edge { float cost; short int type; bool kept; bool skip; int nodeID1; int nodeID2; }; namespace boost { namespace serialization { template<class Archive> void serialize(Archive & ar, Point & v, const unsigned int version) { ar & v.x; ar & v.y; ar & v.z; } template<class Archive> void serialize(Archive & ar, Node & n, const unsigned int version) { ar & n.point; ar & n.maxRadius; ar & n.motionType; ar & n.label; ar & n.ID; } template<class Archive> void serialize(Archive & ar, Edge & e, const unsigned int version) { ar & e.cost; ar & e.type; ar & e.kept; ar & e.skip; ar & e.nodeID1; ar & e.nodeID2; } } // namespace serialization } // namespace boost typedef boost::adjacency_list<boost::setS, boost::vecS, boost::undirectedS, Node, // bundled data Edge, // bundled data boost::no_property, // not needed boost::listS> Graph; typedef boost::graph_traits<Graph>::vertex_iterator NodeIterator; typedef boost::graph_traits<Graph>::edge_iterator EdgeIterator; int main() { Graph g; for(int ID = 0; ID < 1000; ID++) { Node node; node.ID = ID; node.point.x = (float) ID; node.point.y = (float) ID; node.point.z = (float) ID; node.maxRadius = 1.0f; node.motionType = 0; node.label = 0; boost::add_vertex(node, g); } std::pair<NodeIterator, NodeIterator> vertexIterators = boost::vertices(g); NodeIterator nodeIterator1 = vertexIterators.first; for(; nodeIterator1 != vertexIterators.second; nodeIterator1++) { for(NodeIterator nodeIterator2 = nodeIterator1; nodeIterator2 != vertexIterators.second; nodeIterator2++) { if(*nodeIterator1 == *nodeIterator2) continue; Edge edge; edge.cost = 1.0f; edge.kept = true; edge.skip = false; edge.type = 0; edge.nodeID1 = g[*nodeIterator1].ID; edge.nodeID2 = g[*nodeIterator2].ID; boost::add_edge(*nodeIterator1, *nodeIterator2, edge, g); } } std::cout << "Number of nodes = " << boost::num_vertices(g) << std::endl; std::cout << "Number of edges = " << boost::num_edges(g) << std::endl; std::cout << "SAVE!" << std::endl; std::ofstream filename1("binary_serialization.txt"); boost::archive::binary_oarchive binary_oa(filename1); binary_oa & g; filename1.close(); std::cout << "LOAD!" << std::endl; Graph g3; std::ifstream filename2("binary_serialization.txt", std::ios::binary); try { boost::archive::binary_iarchive binary_ia(filename2); binary_ia & g3; // error here }catch (std::exception& e) { std::cout << e.what() << std::endl; } std::cout << "Number of nodes = " << boost::num_vertices(g3) << std::endl; std::cout << "Number of edges = " << boost::num_edges(g3) << std::endl; int a = 0; std::cin >> a; return 0; }

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Re: [Boost-users] in IOS, thread_info object is being destructed before the thread finishes executing (Andy Weinstein)
by Andy Weinstein 06 Feb '13

06 Feb '13

I have solved this problem. Please see my post in stack overflow at: http://stackoverflow.com/questions/14692802/boost-threads-in-ios-thread-inf… The short answer is that the IOS boost.sh script needs to be modified to use BOOST_SP_USE_SPINLOCK instead of BOOST_SP_USE_PTHREADS. But there are a lot of details involved in getting this to work in IOS which are described in that post. Maybe also a small modification to the boost code in spinlock_gcc_arm.hpp, but I need to verify that a change I made along the way is absolutely necessary.

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max value by the number of bits
by Christian Henning 06 Feb '13

06 Feb '13

Hi there, is there a general template for calculating the max value by the number of bits. GIL right now uses the following template: template <int K> struct unsigned_integral_max_value<packed_channel_value<K> > : public mpl::integral_c<typename packed_channel_value<K>::integer_t, (1<<K)-1> {}; This code gives me some compiler errors with clang 3.2. for K = 31, for instance. Ideally I would like to take K up to 64. A small fix gets me up to K = 63 template <int K> struct unsigned_integral_max_value<packed_channel_value<K> > : public mpl::integral_c<typename packed_channel_value<K>::integer_t, (uint64_t(1)<<K)-1> {}; Is there a better way in boost? Thanks, Christian

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[Auto-link] Visual Studio doesn't search for the correct libraries
by Angelo Moscati 06 Feb '13

06 Feb '13

Hi, I recently moved from Boost version 1.49 to 1.52. I want to use the static library versions but the autolink keep to requeire the dynamic one. This is the command line i use to build boost on Windows: set REQUESTED_BOOST_LIBRARIES=--with-serialization --with-thread --with-date_time --with-system --with-regex --with-filesystem --with-log set ADDITIONAL_BOOST_FLAGS=define=BOOST_LOG_NO_COMPILER_TLS rem x86 .\b2 -j 8 link=static runtime-link=static runtime-debugging=on variant=debug threading=multi --abbreviate-paths architecture=x86 --stagedir=stage\x86\debug %ADDITIONAL_BOOST_FLAGS% %REQUESTED_BOOST_LIBRARIES% When i try to build my application, i get the follow errors (it builds fine with Boost 1.49): error LNK1104: cannot open file 'libboost_filesystem-vc100-mt-gd-1_52.lib'. But the library i built is libboost_filesystem-vc100-mt-sgd-1_52.lib. Can you tell me what i do wrong? Thanks, Angelo

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[string.algo] find_iterator, gives compile error in Boost 1.53
by gast128 06 Feb '13

06 Feb '13

Hello all, just dl Boost 1.53 and now I get a compile error in 'find_iterator' when using a forward iterator. Probably related to the change 'increment'. It now uses begin() + 1, and the + operator is not defined for the supplied iterator.

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Archive search
by Angelo Moscati 06 Feb '13

06 Feb '13

Hi, I would like to know if there is a way to search the archive before asking questions. Thanks, Angelo

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[program_options] Is it possible to change semantics after add_options() ?
by lukasz kucharski 06 Feb '13

06 Feb '13

Hello, I would like to ask if it is possible to change value_semantic associated with a program_option after it has been created ? I create `program_options` instance and populate it with add_options. Like in the examples provided by the documentation. I would like to change the semantics of a particular option later on. Is this even possible, or is this functionality deliberately disabled. I figured out that one can use options_description::find(), then strip it out `const`ness and dynamic cast to `typed_value_base` and use its methods. My motivation is such a design. I have a set of applications, which have a common subset of command line options/switches. However, they differ a bit in semantics. I.e. default value. I decided to refactor common parts into some `BasicApp` class and I thought I could move common options along with it as `boost::program_options` OO design should naturally support it. And it worked like a charm with `add_options` semantics to add new options. Up to the point I needed to change existing default values. Is there a proper way to do it ? Removing `const` constraint seems a bad approach since it looks like it's left there on purpose. Or my use-case is ill or hopeless. With regards, Łukasz.

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