February 2011 - Boost-users - lists.preview.boost.org

[regex] Mitigating mischief and malice
by Jim Bell 28 Feb '11

28 Feb '11

Say you wanted to give web users a boost::regex interface to a set of data, knowing that some will try to use it for mischief and malice. I'm vaguely aware that one can write a regex to consume lots of CPU (denial-of-service attack), but also lots of stack and/or memory. What are the risks and how would you address them? Would you filter out certain classes of regular expressions? Tune it via BOOST_REGEX_NON_RECURSIVE and/or other parameters? Would you forbid it altogether? Thanks in Advance, -Jim

3 4

[range] join() and adaptors::transformed do not play nicely with each other
by Nathan Ridge 27 Feb '11

27 Feb '11

Hello, For the following code: #include <vector> #include <boost/range/adaptor/transformed.hpp> #include <boost/range/join.hpp> using boost::adaptors::transformed; using boost::join; int add1(int i) { return i + 1; } int main() { std::vector<int> A, B; auto joined = join(A | transformed(add1), B); } I get the following compiler errors: In file included from ../shared/test/test.cpp:3:0: ../../lib/boost/boost/range/join.hpp: In instantiation of 'boost::range_detail ::joined_type< const boost::range_detail::transformed_range<int (*)(int), vector<int> >, const vector<int> >': ../../lib/boost/boost/range/join.hpp:40:7: instantiated from 'boost ::joined_range< const boost::range_detail::transformed_range<int (*)(int), vector<int> >, const vector<int> >' ../shared/test/test.cpp:13:48: instantiated from here ../../lib/boost/boost/range/join.hpp:34:7: error: no type named 'type' in 'boost::range_detail::demote_iterator_traversal_tag< boost::detail::iterator_category_with_traversal< input_iterator_tag, boost::random_access_traversal_tag >, boost::random_access_traversal_tag >' ../../lib/boost/boost/range/join.hpp: In instantiation of 'boost::joined_range< const boost::range_detail::transformed_range<int (*)(int), vector<int> >, const vector<int> >': ../shared/test/test.cpp:13:48: instantiated from here ../../lib/boost/boost/range/join.hpp:47:11: error: no type named 'type' in 'boost::range_detail::demote_iterator_traversal_tag< boost::detail::iterator_category_with_traversal< input_iterator_tag, boost::random_access_traversal_tag >, boost::random_access_traversal_tag >' What is going on? Thanks, Nate.

2 1

[range] joining ranges with different value types, then transforming with a polymorphic functor
by Nathan Ridge 27 Feb '11

27 Feb '11

Hello, I would like to do the following with Boost.Range: #include <vector> #include <boost/range/adaptor/transformed.hpp> #include <boost/range/join.hpp> #include <boost/foreach.hpp> using boost::adaptors::transformed; using boost::join; struct A { int x; }; struct B { int x; }; struct C { int x; }; struct to_C { C operator()(A a) const { return C{a.x}; } C operator()(B b) const { return C{b.x}; } }; int main() { std::vector<A> a; std::vector b; BOOST_FOREACH(const C& c, join(a, b) | transformed(to_C())) { // do something } return 0; } Basically, I am joining two ranges with different value types (A and B), then transforming the resulting range with a polymorphic functor (to_C) that converts either of A or B to a common third type, C. When I try to loop through this resulting range, however, I get the following compiler errors: In file included from ../../lib/boost/boost/range/join.hpp:15:0, from test.cpp:3: ../../lib/boost/boost/range/detail/join_iterator.hpp: In member function 'A & boost::range_detail::join_iterator_union< vector<A>::iterator, vector::iterator, A & >::dereference(unsigned int) const': ../../lib/boost/boost/range/detail/join_iterator.hpp:216:42: instantiated from 'boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >::A & boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >::dereference() const' ../../lib/boost/boost/iterator/iterator_facade.hpp:517:32: instantiated from 'static boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >::A & boost::iterator_core_access::dereference( const boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag > & )' ../../lib/boost/boost/iterator/iterator_facade.hpp:643:67: instantiated from 'boost::iterator_facade<I, V, TC, R, D>::A & boost::iterator_facade< I, V, TC, R, D >::operator *() const' ../../lib/boost/boost/iterator/transform_iterator.hpp:121:31: instantiated from 'boost::detail::transform_iterator_base< to_C , boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >, boost::use_default, boost::use_default >::type::C boost::transform_iterator< UnaryFunction , boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >, boost::use_default, boost::use_default >::dereference() const' ../../lib/boost/boost/iterator/iterator_facade.hpp:517:32: instantiated from 'static boost::transform_iterator< to_C , boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >, boost::use_default, boost::use_default >::C boost::iterator_core_access::dereference( const boost::transform_iterator< to_C , boost::range_detail::join_iterator< vector<A>::iterator, vector::iterator, A, A & , boost::random_access_traversal_tag >, boost::use_default, boost::use_default > & )' ../../lib/boost/boost/iterator/iterator_facade.hpp:643:67: instantiated from 'boost::iterator_facade< I, V, TC, R, D >::C boost::iterator_facade<I, V, TC, R, D>::operator *() const' ../../lib/boost/boost/foreach.hpp:748:58: instantiated from 'boost ::foreach_detail_::foreach_reference< boost::range_detail::transformed_range< to_C, const boost::joined_range<vector<A>, vector > >, mpl_::bool_<true> >::ame boost::foreach_detail_::foreach_reference<T, C>::type = C boost ::foreach_detail_::deref( boost::foreach_detail_::const boost::foreach_detail_::auto_any_base & , boost::foreach_detail_::type2type< boost::range_detail::transformed_range< to_C, const boost::joined_range<vector<A>, vector > >, mpl_::bool_<true> > * )' test.cpp:23:5: instantiated from here ../../lib/boost/boost/range/detail/join_iterator.hpp:71:37: error: no match for ternary 'operator?:' in '(selected != 0u) ? this->boost::range_detail ::join_iterator_union<vector<A>::iterator, vector::iterator, A &> ::m_it2.vector<A>::iterator::operator *() : this->boost::range_detail ::join_iterator_union<vector<A>::iterator, vector::iterator, A &> ::m_it1.vector<A>::iterator::operator *()' Is there a way to do this? Thanks, Nate.

2 1

BGL - color map assertion failed
by Krisztian Sinka 27 Feb '11

27 Feb '11

Hi, I have the following code using Boost Graph Library to use the breadth-first-search: -------- code start -------- template<typename T> class MyVisitor : public boost::default_bfs_visitor{ public: MyVisitor(T& d): boost::default_bfs_visitor(),d_(d) {}; template<typename E, typename G> void tree_edge(E e,const G& g) const { typedef typename boost::graph_traits<G>::vertex_descriptor VD; VD u = boost::source(e,g); VD v = boost::target(e,g); d_[u].parent_ = v; }; private: T& d_; }; ... typedef boost::adjacency_list<boost::listS // out-edges , boost::vecS // vertex set , boost::undirectedS , boost::property<boost::vertex_name_t,IndexT> , boost::property<boost::edge_name_t,IndexT> > GraphT; ... typedef boost::graph_traits<GraphT>::vertex_descriptor VD; ... struct DataMap { DataMap(VD p):parent_(p),distance_(0){}; DataMap():parent_(0),distance_(0){}; VD parent_; int distance_; }; ... typedef std::vector<DataMap> VisitedT; typedef VisitedT::iterator VisitedIterT; // Graph g properly initialized here VisitedT visited(boost::num_vertices(g)); for(VI i=vertices(g).first,iend=vertices(g).second;i!=iend;++i){ visited[*i].parent_=*i; }; MyVisitor<VisitedT> vis(visited); boost::breadth_first_search(g,boost::vertex(0,g),boost::visitor(vis)); -------- code end -------- The compiles OK, but when I run it I got: Assertion failed: (std::size_t)i < pm.n, file C:/boost_1_46_0/boost/graph/two_bit_color_map.hpp, line 86 which is strange as I do not tweak with the color map. From the trials it seems that the "VisitedT" works if it holds "simple" types like vertex decriptor etc and not aggregates. My intention with the DataMap to register the vertex parents and the vertex distance at the same time, when the edge is visited. Is there any limit on the library side or did I something wrong? Thank you and regards, K

2 1

[lexical_cast] locale dependent result?
by Alexander Lamaison 27 Feb '11

27 Feb '11

Is the result of lexical_cast<std::string> locale-dependent? One of my contributors has submitted a fix for a problem he says is caused by lexical_cast adding commas to a port number, e.g.: 65535 becomes "65,535". I'm unable to reproduce this but it may be something specific to his locale. If this is the case, what would be the correct way to get a canonical, locale-independent string from an integer? Thanks. Alex -- Easy SFTP for Windows Explorer (http://www.swish-sftp.org)

1 0

[Review] Phoenix V3: Mini-review starts February 20th
by Hartmut Kaiser 27 Feb '11

27 Feb '11

Hi all, Thomas Heller worked hard to address the outstanding issues of the original Phoenix review. He ported Phoenix to Boost.Proto. As mandated by the original Boost review, we will conduct a mini-review of his Phoenix V3 library. This mini-review starts today, February 20th, 2011 and ends on March 2nd, 2011. ------------------ About the library: The Phoenix library enables FP techniques such as higher order functions, lambda (unnamed functions), currying (partial function application) and lazy evaluation in C++. The focus is more on usefulness and practicality than purity, elegance and strict adherence to FP principles. Phoenix is a very important infrastructure library. It is currently a utility library included with Spirit V2 and therefore is already available for years from the latest Boost distributions (headers: $BOOST_ROOT/boost/spirit/home/phoenix, docs: $BOOST_ROOT/libs/spirit/phoenix, or http://www.boost.org/doc/libs/1_45_0/libs/spirit/phoenix/index.html) ------------------ The code of new Phoenix V3 (that's what we mini-review) can be found at: https://svn.boost.org/svn/boost/sandbox/SOC/2010/phoenix3/ the documentation is at: http://svn.boost.org/svn/boost/sandbox/SOC/2010/phoenix3/libs/phoenix/doc/ht ml/index.html ------------------ Here are the questions raised during the initial review of Phoenix in September 2008 (see here: http://thread.gmane.org/gmane.comp.lib.boost.devel/180753) <quote> We will have a mini review before Phoenix gets merged to SVN to make sure whether the feedback from the v2 review was accommodated. Additionally this review will have to discuss: - the breaking interface changes from v2 - the migration path from boost::bind and lambda to Phoenix - how the interoperability with std::bind is solved (result_of semantics) - C++0x features such as rvalue references and variadic templates - the new extensibility mechanism - unified placeholders and interoperability issues with other Proto-based DSELs (such as Spirit.Qi, Spirit.Karma, and Xpressive) - compile times </quote> Please note that Phoenix already has been accepted as a Boost library. We don't vote about that anymore. The purpose of this mini-review is to discuss if the newly rewritten Phoenix V3 addresses the outstanding issues from the main review. In the end I will have to make the decision whether to include the new library into SVN trunk. I really hope to see your participation in the discussions on the Boost mailing lists! Regards Hartmut Review Manager --------------- http://boost-spirit.com

5 18

[dateTime] construting a date with time
by Sean Farrow 27 Feb '11

27 Feb '11

Hi: I'm currently doing some work with the boost date time library. Can the boost date class be constructed with a time, or do I need a separate time variable as well? If so, should I use a local time, or posix time, given that the time has already been converted from utc to the users timezone. Any help appreciated. Regards Sean.

2 1

[Review] Phoenix V3: mini-review starts February 19th
by Hartmut Kaiser 27 Feb '11

27 Feb '11

Hi List, Phoenix V3 is nearing its completion. With the port to Boost.Proto we tried to address the outstanding issues of the review and would like to announce that the mini-review will start on February 19th. Feel free to preview the code at: https://svn.boost.org/svn/boost/sandbox/SOC/2010/phoenix3/ and the documentation at: http://svn.boost.org/svn/boost/sandbox/SOC/2010/phoenix3/libs/phoenix/doc/ht ml/index.html We are currently occupied with code cleanups and finishing of the documentation. The code itself is in a stable condition, feel free to make yourself comfortable with this new library. Regards Hartmut Phoenix V3 Review Manager --------------- http://boost-spirit.com

9 17

[Filesystem] V3 interface inconsistency
by Peter Klotz 27 Feb '11

27 Feb '11

Hello I came across the following interface inconsistency in Boost.Filesystem V3 (Boost 1.46.0) in boost::filesystem::path Windows: const std::string string() const std::wstring& wstring() Linux: const std::string& string() const std::wstring wstring() We converted V2 code looking like this (necessary since filename() in V3 returns a path instead of a string): const std::string& filename=path.filename(); The converted V3 code: const std::string& filename=path.filename().string(); Obviously this code crashes in Linux since filename() returns a temporary object and string() returns a reference to one of its members. However this code works in Windows due to the different return types. My question: Wouldn't it make sense for all methods to return a value instead of a reference? It would ease the transition from V2 to V3 and avoid subtle programming errors. Regards, Peter.

3 3

[Serialization] Testing if a provided file is actually a serialized archive
by Cedric Laczny 26 Feb '11

26 Feb '11

Hi, I would like to know if there exists a way to check for a given file if it is actually a serialized archive or a pure txt-file, at best without the need to read in that file completely. At the moment, I use boost::serialization to store self-defined class-instances in txt-files, so using something like the system's "file"-command would not bring me far. Now I would like my program to distinguish if the provided input-argument is a text-file that needs to be parsed or if it can simply restore this previous instance. Of course, using a separate option indicating if an archive was passed would work, but IMHO is not very beautiful. Best, Cedric

2 1