June 2007 - Boost-users - lists.preview.boost.org

boost:array lacks a statically-checked get()
by Benoit Hudson 06 Jun '07

06 Jun '07

Reading the archives, I see that the idea of adding a template <unsigned i> T get(); function to boost::array has been somewhat summarily rejected as unnecessary: http://lists.boost.org/boost-users/2005/08/12983.php et seq. And yet I'm finding myself wanting it repeatedly. Here are three places I've seen it crop up: (1) My current application is an arbitrary-dimensional geometry code. I want it to be a template argument what dimension we live in (2, 3, 4, ...). In d dimensions, a simplex has d+1 vertices on it, a point has d coordinates, and an face is a (d-1)-dimensional simplex that has d vertices. You can imagine the potential for off-by-one bugs (personally, I need not imagine). These get caught at runtime when using the array operator[], but I'd rather they be caught at compile time when possible. Therefore, when I'm feeling caffeinated, I write the appropriate BOOST_STATIC_ASSERT (which is of course itself sometimes off by one). (2) I've seen (and written) rather a lot of GUI, networking, and cross-language glue where a common idiom is to have an array of function pointers. Sometimes, the 'name' of the function is an integer read in at runtime. Sometimes, it is known at compile-time. Typically I've seen this implemented using an enum; calling function i is then functions[i](args), whereas calling function foo is functions[FOO](args). The former one can only be checked at run-time. The latter one should be checked at compile-time. It's fine for me to force me to write it as functions.get<FOO>(args) to get compile-time checking, but I do not want to be forced to change both entry FOO in the array, and every call to foo() elsewhere, if I change the name of the function (i.e. during debugging). When I've done this in the past, I've been living in C-land or C++ without boost, so the idea of compile-time checking didn't even occur to me (and, of course, bugs cropped up all the time). (3) Sometimes I don't need an array at all -- I just want a tuple with all values the same type. It's far handier to declare that type as array<foo, 4> than as tuple<foo, foo, foo, foo>. Also, we can now also use the uber-delicious BOOST_FOREACH on the array, which can't be done on the tuple. Summarizing: whenever a client wants to use both integers and names to access a field, array::get<> is useful and matches the boost philosophy of compile-time checking over runtime checking. The change is small in terms of LOC, and does not affect any code outside this one function (and, as far as I can determine, is even ABI-compatible with the prior array code). The runtime implication is nil. -- Benoît

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[serialization] Wrapper + make_nvp woes
by Dan Thill 06 Jun '07

06 Jun '07

Greetings, I have a need to serialize plain old C character arrays as strings within the xml and text archive types. By default, these are serialized element by element. I've read the previous messages on the list on the perils of doing such (buffer overflows), and I hit across a somewhat acceptable solution using serialization wrappers. I'm new to all of this, so I based my implementation off of "nvp" and "binary_object" ------------------------------- struct char_array { char* const m_t; const std::size_t m_size; template<class Archive> void save(Archive & ar, const unsigned int /* file_version */) const { const std::string t(m_t); ar.operator<<(t); } template<class Archive> void load(Archive & ar, const unsigned int /* file_version */) const { std::string t; ar.operator>>(t); scASSERT_MSG(t.size() < m_size, "A corruption occurred"); strncpy(const_cast<char*>(m_t), t.c_str(), m_size); } BOOST_SERIALIZATION_SPLIT_MEMBER() explicit char_array( char* const t, std::size_t size) : m_t(t), m_size(size) {} char_array(const char_array & rhs) : m_t(rhs.m_t), m_size(rhs.m_size) {} }; ----------------------------------------------- The premise is simple, probably naive, and not too efficient: Convert each char[] to a std::string, and serialize that. Loading is just the reverse. However, I keep getting a compile time exception in the xml archive loading code. This is with Boost 1.33, VC8. 1>c:\Boost\include\boost-1_33_1\boost/archive/basic_xml_oarchive.hpp(86) : error C2027: use of undefined type 'boost::STATIC_ASSERTION_FAILURE<x>' 1> with 1> [ 1> x=false 1> ] 1> c:\Boost\include\boost-1_33_1\boost/archive/detail/interface_oarchive.hpp(78) : see reference to function template instantiation 'void boost::archive::basic_xml_oarchive<Archive>::save_override<T>(T &,int)' being compiled 1> with 1> [ 1> Archive=boost::archive::xml_oarchive, 1> T=const std::string 1> ] 1> d:\SDEV8\SOURCE\include\sc_s11n/char_array.h(49) : see reference to function template instantiation 'Archive &boost::archive::detail::interface_oarchive<Archive>::operator <<<const std::string>(T &)' being compiled 1> with 1> [ 1> Archive=boost::archive::xml_oarchive, 1> T=const std::string 1> ] It seems as if, after serializing the nvp object, it's expecting an nvp object around the std::string. Is there a way that I can call the default serialization for std::string from my char_array wrapper, without having it go through the normal xml specializations which require it to be part of an nvp? I'm new with this, so please be gentle. I've consumed almost the entire list archive and I can't come up with a fix. Thanks, Dan

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[serialization]: text (xml) iarchive - format options for integers?
by Frank Bergemann 06 Jun '07

06 Jun '07

Hi, can i make xml_iarchive accept "0x11" instead of "17" for an int type data element? Or do i have to derive my own iarchive and implement that myself? \Frank _______________________________________________________________ SMS schreiben mit WEB.DE FreeMail - einfach, schnell und kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192

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[Graph] remove edges and reinsert them
by Dominik Heide 06 Jun '07

06 Jun '07

Hi there, I want to delete a vertex from a graph and later reinsert it again. I did this by removing all edges from that vertex and later adding the edges again. But the behavior of the program quite strange. First, I use a undirected adjacancy list typedef adjacency_list<vecS, vecS, undirectedS, no_property, no_property> Graph; When, use Graph g, gs; // set g typename graph_traits<GraphT>::vertex_iterator vi, ve, vii, vei; typename graph_traits<GraphT>::out_edge_iterator out_i, out_end, tmp; for( tie(vi, ve) = vertices(g); vi != ve; vi++) { gs = g; clear_vertex( *vi, g) // some code g = gs; } everything is fine. I don't want to save the whole graph since I only delete a couple of edges. Therefore, I did vector<typename graph_traits<GraphT>::vertex_descriptor> deletedEdges; typename vector<typename graph_traits<GraphT>::vertex_descriptor>::iterator dei; typename graph_traits<GraphT>::vertex_iterator vi, ve, vii, vei; typename graph_traits<GraphT>::out_edge_iterator out_i, out_end, tmp; ... for( tie(vi, ve) = vertices(g); vi != ve; vi++) { for( tie( out_i, out_end ) = out_edges( *vi, g); out_i != out_end; out_i++) { deletedEdges.push_back(target(*out_i, g)); } clear_vertex( *vi, g) // some code for(dei = deletedEdges.begin(); dei < deletedEdges.end(); ++dei) { add_edge( *vi, *dei, g); } } This code does not restore the graph completely. Although it looks the same the shortest paths are different to the ones with the above code. Is there something about clear_vertex() I don't know and therefore don't restore corectly? Any help appreachiated, Thank you, Dominik

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[BGL] topological_sort compile error
by David A. Greene 05 Jun '07

05 Jun '07

Hi everyone, I'm having trouble with BGL's (Boost 1.33.1) topological sort. In my source code I have this simple call: std::vector<my_vertex> rev_topo_order; topological_sort(*t, std::back_inserter(rev_topo_order)); Here "t" is an iterator to a list of graphs declared like this: typedef boost::adjacency_list< boost::setS, // Out edge list type boost::listS, // Vertex list type boost::bidirectionalS, // Needed for DAG, topo sort my_property_bundle // Vertex properties > my_graph_type; The error trace below is mostly gobbledygook to me, but it looks like it's running into trouble with BGL's default bgl_named_params. The call chain runs through this curious bit of code: template <typename VertexListGraph, typename OutputIterator> void topological_sort(VertexListGraph& g, OutputIterator result) { topological_sort(g, result, bgl_named_params<int, buffer_param_t>(0)); // bogus } That looks...interesting to me. What's with the "bogus" comment? Any idea what's going on here? Any more information I can provide that would be helpful? The gmane archives show that Renaud Lepere ran into this problem in August '06 but I can't find any replies to his question. He gave a small example which I've confirmed reproduces the problem with g++ 4.1.2: #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/depth_first_search.hpp> #include <boost/graph/visitors.hpp> #include <boost/graph/topological_sort.hpp> #include <iterator> typedef boost::adjacency_list<boost::vecS, boost::listS, boost::bidirectionalS, int, int > Graph; typedef boost::graph_traits<Graph>::vertex_descriptor Vertex; typedef std::vector< Vertex > Vertices; int main() { Graph g; Vertices vs; boost::topological_sort(g, back_inserter(vs)); } Thanks for any help you can give. -Dave ---------------------- Error trace ---------------------- ./boost-1_33_1/boost/property_map.hpp: In member function 'R boost::iterator_property_map<RandomAccessIterator, IndexMap, T, R>::operator[](typename boost::property_traits<IndexMap>::key_type) const [with RandomAccessIterator = __gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, IndexMap = boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, T = boost::default_color_type, R = boost::default_color_type&]': ./boost-1_33_1/boost/property_map.hpp:319: instantiated from 'void boost::put(const boost::put_get_helper<Reference, PropertyMap>&, K, const V&) [with PropertyMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, boost::default_color_type, boost::default_color_type&>, Reference = boost::default_color_type&, K = void*, V = boost::default_color_type]' ./boost-1_33_1/boost/graph/depth_first_search.hpp:197: instantiated from 'void boost::depth_first_search(const VertexListGraph&, DFSVisitor, ColorMap, typename boost::graph_traits<G>::vertex_descriptor) [with VertexListGraph = boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, DFSVisitor = boost::topo_sort_visitor<std::back_insert_iterator<std::vector<void*, std::allocator<void*> > > >, ColorMap = boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, boost::default_color_type, boost::default_color_type&>]' ./boost-1_33_1/boost/graph/depth_first_search.hpp:246: instantiated from 'static void boost::detail::dfs_dispatch<boost::detail::error_property_not_found>::apply(const VertexListGraph&, DFSVisitor, Vertex, const boost::bgl_named_params<P, T, R>&, boost::detail::error_property_not_found) [with VertexListGraph = boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, Vertex = void*, DFSVisitor = boost::topo_sort_visitor<std::back_insert_iterator<std::vector<void*, std::allocator<void*> > > >, P = boost::topo_sort_visitor<std::back_insert_iterator<std::vector<void*, std::allocator<void*> > > >, T = boost::graph_visitor_t, R = boost::bgl_named_params<int, boost::buffer_param_t, boost::no_property>]' ./boost-1_33_1/boost/graph/depth_first_search.hpp:324: instantiated from 'void boost::depth_first_search(const VertexListGraph&, const boost::bgl_named_params<P, T, R>&) [with VertexListGraph = boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, P = boost::topo_sort_visitor<std::back_insert_iterator<std::vector<void*, std::allocator<void*> > > >, T = boost::graph_visitor_t, R = boost::bgl_named_params<int, boost::buffer_param_t, boost::no_property>]' ./boost-1_33_1/boost/graph/topological_sort.hpp:64: instantiated from 'void boost::topological_sort(VertexListGraph&, OutputIterator, const boost::bgl_named_params<P, T, R>&) [with VertexListGraph = boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, OutputIterator = std::back_insert_iterator<std::vector<void*, std::allocator<void*> > >, P = int, T = boost::buffer_param_t, R = boost::no_property]' ./boost-1_33_1/boost/graph/topological_sort.hpp:70: instantiated from 'void boost::topological_sort(VertexListGraph&, OutputIterator) [with VertexListGraph = boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, OutputIterator = std::back_insert_iterator<std::vector<void*, std::allocator<void*> > >]' [ User code instantiations snipped] ./boost-1_33_1/boost/property_map.hpp:349: error: no match for 'operator+' in '((const boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, boost::default_color_type, boost::default_color_type&>*)this)->boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, boost::default_color_type, boost::default_color_type&>::iter + boost::get [with PropertyMap = boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, Reference = const boost::detail::error_property_not_found&, K = void*](((const boost::put_get_helper<const boost::detail::error_property_not_found&, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t> >&)((const boost::put_get_helper<const boost::detail::error_property_not_found&, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t> >*)(&((const boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, boost::default_color_type, boost::default_color_type&>*)this)->boost::iterator_property_map<__gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >, boost::adj_list_vertex_property_map<boost::adjacency_list<boost::setS, boost::listS, boost::bidirectionalS, myclass::my_property_bundle, boost::no_property, boost::no_property, boost::listS>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t>, boost::default_color_type, boost::default_color_type&>::index))), ((void* const&)((void* const*)(& v))))' ./lib/gcc/i686-pc-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/stl_iterator.h:703: note: candidates are: __gnu_cxx::__normal_iterator<_Iterator, _Container> __gnu_cxx::__normal_iterator<_Iterator, _Container>::operator+(const typename std::iterator_traits<_Iter>::difference_type&) const [with _Iterator = boost::default_color_type*, _Container = std::vector<boost::default_color_type, std::allocator<boost::default_color_type> >] ./lib/gcc/i686-pc-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/stl_bvector.h:353: note: std::_Bit_const_iterator std::operator+(ptrdiff_t, const std::_Bit_const_iterator&) ./lib/gcc/i686-pc-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/stl_bvector.h:267: note: std::_Bit_iterator std::operator+(ptrdiff_t, const std::_Bit_iterator&)

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Newbie question: IPC
by Stew Paddaso 05 Jun '07

05 Jun '07

Does boost currently provide facilities for named pipes and/or shared memory between processes? I didn't see any reference to it after looking at this webpage: http://www.boost.org/libs/libraries.htm After doing a Google search, I noticed that the shmem library appears to have been accepted after review, but it is not listed on the page I referenced above. Thanks.

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Boost Python: Howto wrap "out" arguments of a methode
by Alexander Eisenhuth 05 Jun '07

05 Jun '07

How to wrap methode Get with Boost.Python? class MyClass { public: MyClass(); void GetX(double &pos_x); [...] I'v tried it with: .def( "GetX" , &::MyClass::GetX , bp::arg("") , bp::return_value_policy<bp::return_arg<1>() >() But when I try it in python: Boost.Python.ArgumentError: Python argument types in MyClass.GetX(MyClass, int) did not match C++ signature: GetX(class MyClass::LedPosition_C {lvalue}, int {lvalue} ) Any ideas? Thanks Alexander

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[boost.intrusive] Assertion failure with SunCC
by Zeljko Vrba 05 Jun '07

05 Jun '07

The following simple program crashes with assertion failure when compiled under Solaris 11 with SunCC: Sun C++ 5.8 Patch 121018-10 2007/02/21 Assertion failed: node_algorithms::unique(to_insert), file boost/boost/intrusive/list.hpp, line 168 I'm using the latest Boost.Intrusive from CVS (snapshot taken 2007-06-03). I have tracked the problem, but I don't know wheter it's the code or compiler problem; see below the code for cause. == Begin code // Program to demonstrate a bug with SunCC and member hooks. #include <boost/intrusive/list.hpp> struct klass { void *data_klass; boost::intrusive::list_member_hook<> hook_; typedef boost::intrusive::list< boost::intrusive::list_member_hook<>::value_traits< klass, &klass::hook_>, false> list; }; static klass Gd; static klass::list Gl; int main(void) { => Gl.push_back(Gd); return 0; } == End code When the program is started, the hook's prev_ and next_ members are initialized correctly to &Gd.hook_ (0x8062dd8). The member_value_traits instance is by dbx resolved to boost::intrusive::detail::member_value_traits< klass,boost::intrusive::list_member_hook< (boost::intrusive::linking_policy)1,void*>, klass::hook_>::to_node_ptr ^^^^^^^^^^^^ Corresponds to the template P parameter. The statement MemberHookType* result = &(value.*P); sets result to 0x8062dd4 (4 bytes off from the hooks address). Finally, in push_back method, the to_insert value receives 0x8062dd4 which equals &Gd (ie. it points to the start of the object) instead of &Gd.hook_. Should this be reported as a compiler bug? BTW, I'll try using base hooks as a workaround. (PS: the code works fine with gcc4.2)

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lib folder?
by Mike Wyatt 05 Jun '07

05 Jun '07

I just installed MinGW and Boost. The boost_1_34_0 folder I extracted from the downloaded zip did not contain a "lib" folder, which is referred to in the Getting Started for Windows guide (http://www.boost.org/more/getting_started/windows.html) I've already built all the Boost libraries, so I'm guessing that I need to copy the lib folder from the new stage folder into the boost root. Is that correct? Also, I built bjam with the "mingw" toolset, and Boost with "gcc". Is that a problem? Here are the commands I ran: *Building bjam*: c:\Program Files\boost_1_34_0\tools\jam\src\build mingw *Building Boost*: c:\Program Files\boost_1_34_0\bjam --build-dir=build --toolset=gcc stage Does that make sense? Am I doing everything right, so far?

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Boost 1.34 and VC++ x64
by Cory Nelson 05 Jun '07

05 Jun '07

This was pretty straightforward for 1.33, but 1.34 using BB2 seems to have changed things a bit. There doesn't seem to be any documentation on compiling 1.34 for x64 with VC++ - can anyone offer some insight?

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