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handling exceptions in Boost threads
by Steve McKay 05 Jan '05

05 Jan '05

Is there a generally accepted way to handle exceptions in Boost threads? I have a main thread which spawns 4 children and waits for them all to finish with boost::thread_group::join_all. I want to know if any of them threw an exception (which I would catch within the child thread before returning from that thread). Steve F. McKay Social Security Administration Room 760 Altmeyer 6401 Security Boulevard Baltimore, Maryland 21235 (410)965-3014

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a question on boost::is_function
by Kevin Lee 05 Jan '05

05 Jan '05

should the following code return: true or false? boost::is_function<int (*)(int)>::value if the result is false, why? I don't understand it. if the result is true, the code of boost_1_32_0/libs/type_traits/test/is_function_test.cpp line 42 expect it to be false. could someone help me with this? ----------------------------------------- This message and its attachments may contain privileged and confidential information. If you are not the intended recipient(s), you are prohibited from printing, forwarding, saving or copying this email. If you have received this e-mail in error, please immediately notify the sender and delete this e-mail and its attachments from your computer.

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question about breadth_first_search
by Matthias Linkenheil 05 Jan '05

05 Jan '05

Dear all, i want to use the breadth_first_search algorithm to store the visited nodes e.g. in a list for access in the main function. Has anyone an idea to handle this? In my code i print out the visited nodes. The examples in the Boost User Guide about the visitor concept are sometimes not so easy to understand. ... using namespace boost; template <typename VertexNameMap> class bfs_name_printer:public default_bfs_visitor { public: bfs_name_printer(VertexNameMap n_map) : m_name_map(n_map){} template <typename Vertex, typename Graph> void discover_vertex(Vertex u, const Graph& ) const { std::cout<<get(m_name_map, u) <<" "; } private: VertexNameMap m_name_map; }; ... main(){ ... typedef property_map<Graph, vertex_index_t>::type VertexNameMap; VertexNameMap id = get(vertex_index, g); bfs_name_printer<VertexNameMap> vis(id); breadth_first_search(fg, s, visitor(vis)); ... Regards, Matthias

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read_write_mutex assertion on multiprocessor Wintel
by jkharris7＠comcast.net 05 Jan '05

05 Jan '05

As I reported earlier, read_write_mutex asserts in debug mode (VC71), apparently seeing false wake-ups on a condition variable. I was able to do this with just a simple group of threads locking a RWM in tight loops, with one writer and a few readers. The new information is that I am runing this on a dual-Xeon with hyper-threading enabled (so four apparent CPU's), and I'm thinking that maybe boost libs don't get exercised on this kind of hardware very much. Is is possible that a condition::notify_all() happens on each processor? Has anyone else seen this? For now, I just removed the asserts and rebuilt. Synchronization seems to be unaffected in my real-world stress test of RWM. jh

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Boost::filesystem : possible addition
by Georgios Diamantopoulos 05 Jan '05

05 Jan '05

Hello, I've always wanted some functionality to determine the relative path between two paths. Maybe something like this can be added to the convinience.hpp or otherwise: fs::path relative_path_of(fs::path const &base, fs::path const &full) { std::string fullStr = full.string(); std::string baseStr = base.string() + "/"; // add a slash so that it returns the relative path boost::erase_first(fullStr, baseStr); return fs::path(fullStr); } Cheers, Georgios

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Problem serializing (restoring) through base pointer
by Bill Lear 05 Jan '05

05 Jan '05

I have spent several hours combing the documentation and archives, but can't seem to find an answer to my problem. I have an abstract base class, Operation with a pure virtual function 'double value() = 0'. I derive a class, BinaryOperation from Operation. It takes as arguments an operation type (+, -, *, /) and two Operation pointers --- one for the left operand, one for the right. It stores these two pointers internally and uses them when the value() method is invoked. I derive two more classes from Operation, trivial, made-up, useless ones. One is called IncrementOperation, one is called DecrementOperation. I can save to an XML archive properly, but when I try to restore, it core dumps. I am running gcc-3.2. I have tried everything I can think of, but am stuck. I have tried using polymorphic_xml_iarchive (and corresponding output version), but it still fails. The first few stack frames from GDB are: #0 0x0808897f in ?? () #1 0x08052f7d in boost::archive::detail::basic_iarchive::load_pointer(void*&, boost::archive::detail::basic_pointer_iserializer const*, boost::archive::detail::basic_pointer_iserializer const* (*)(boost::serialization::extended_type_info const&)) () #2 0x0804c78a in boost::archive::detail::load_pointer_type<boost::archive::xml_iarchive, Operation*>::invoke(boost::archive::xml_iarchive&, Operation*&) ( ar=@0xbffff0e0, t=@0xbffff330) at /usr/local/include/boost-1_32/boost/archive/detail/iserializer.hpp:450 #3 0x0804c51a in load<boost::archive::xml_iarchive, Operation*> ( ar=@0xbffff0e0, t=@0xbffff330) at /usr/local/include/boost-1_32/boost/archive/detail/iserializer.hpp:529 Following my sig, I've posted the xml input file that is generated by the save, and then following that, the C++ code (fairly short). It is failing on the following line: ia & BOOST_SERIALIZATION_NVP(t); Any help would be appreciated. Thanks. Bill <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="3"> <t class_id="1" class_name="BinaryOperation" tracking_level="1" version="0" object_id="_0"> <Operation class_id="0" tracking_level="1" version="0" object_id="_1"></Operation> <_op>42</_op> <_left_operand class_id_reference="1" object_id="_2"> <Operation object_id="_3"></Operation> <_op>43</_op> <_left_operand class_id="2" class_name="IncrementOperation" tracking_level="1" version="0" object_id="_4"> <Operation object_id="_5"></Operation> <_init>33</_init> </_left_operand> <_right_operand class_id="3" class_name="DecrementOperation" tracking_level="1" version="0" object_id="_6"> <Operation object_id="_7"></Operation> <_init>333</_init> </_right_operand> </_left_operand> <_right_operand class_id_reference="1" object_id="_8"> <Operation object_id="_9"></Operation> <_op>45</_op> <_left_operand class_id_reference="3" object_id="_10"> <Operation object_id="_11"></Operation> <_init>444</_init> </_left_operand> <_right_operand class_id_reference="2" object_id="_12"> <Operation object_id="_13"></Operation> <_init>44</_init> </_right_operand> </_right_operand> </t> </boost_serialization> #include <string> #include <iomanip> #include <iostream> #include <fstream> #include <stdexcept> #include <boost/serialization/nvp.hpp> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> //#include <boost/archive/polymorphic_xml_iarchive.hpp> //#include <boost/archive/polymorphic_xml_oarchive.hpp> #include <boost/serialization/export.hpp> class Operation { public: Operation() { } virtual ~Operation() { } virtual double value() = 0; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ } }; BOOST_IS_ABSTRACT(Operation); class BinaryOperation: public Operation { public: BinaryOperation() : _op(' '), _left_operand(0), _right_operand(0) { } BinaryOperation(char op, Operation* left_operand, Operation* right_operand) : _op(op), _left_operand(left_operand), _right_operand(right_operand) { } virtual ~BinaryOperation() { } virtual double value() { switch (_op) { case '+': return _left_operand->value() + _right_operand->value(); break; case '-': return _left_operand->value() - _right_operand->value(); break; case '*': return _left_operand->value() * _right_operand->value(); break; case '/': return _left_operand->value() / _right_operand->value(); break; } } protected: char _op; Operation* _left_operand; Operation* _right_operand; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Operation) & BOOST_SERIALIZATION_NVP(_op) & BOOST_SERIALIZATION_NVP(_left_operand) & BOOST_SERIALIZATION_NVP(_right_operand); } }; BOOST_CLASS_EXPORT_GUID(BinaryOperation, "BinaryOperation"); class IncrementOperation : public Operation { public: IncrementOperation() : _init(0) { } IncrementOperation(double init) : _init(init) { } virtual double value() { return _init++; } protected: double _init; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Operation) & BOOST_SERIALIZATION_NVP(_init); } }; BOOST_CLASS_EXPORT_GUID(IncrementOperation, "IncrementOperation"); class DecrementOperation : public Operation { public: DecrementOperation() : _init(0) { } DecrementOperation(double init) : _init(init) { } virtual double value() { return _init--; } protected: double _init; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* file_version */){ ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Operation) & BOOST_SERIALIZATION_NVP(_init); } }; BOOST_CLASS_EXPORT_GUID(DecrementOperation, "DecrementOperation"); void save_Operation(const Operation* t) { std::ofstream ofs("operation.xml"); assert(ofs.good()); boost::archive::xml_oarchive oa(ofs); //boost::archive::polymorphic_xml_oarchive oa(ofs); oa & BOOST_SERIALIZATION_NVP(t); } void restore_Operation(Operation*& t) { std::ifstream ifs("operation.xml"); if (!ifs.good()) { throw std::runtime_error("No input archive file"); } boost::archive::xml_iarchive ia(ifs); //boost::archive::polymorphic_xml_iarchive ia(ifs); std::cout << "Reading ...\n"; ia & BOOST_SERIALIZATION_NVP(t); std::cout << "Done reading ...\n"; } int main(int, char *[]) { try { Operation* a = new BinaryOperation('+', new IncrementOperation(33), new DecrementOperation(333)); Operation* b = new BinaryOperation('-', new DecrementOperation(444), new IncrementOperation(44)); Operation* c = new BinaryOperation('*', a, b); save_Operation(c); Operation* new_c; std::cout << "Restoring\n"; restore_Operation(new_c); } catch (std::exception e) { std::cerr << e.what() << '\n'; return 1; } return 0; }

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why doesn't scoped_ptr have a custom deleter?
by Pablo Aguilar 04 Jan '05

04 Jan '05

Hi, I'm currently playing around with Apache's Xerces XML library, and found myself needing to ->release some pointers. shared_ptr + mem_fn works great: shared_ptr<DOMBuilder> db( impl->createBuilder() , mem_fn(&DOMBuilder::release) ); But for the objects I'm using, I don't need a shared_ptr, but just a scoped_ptr. So I'm wondering about the rationale behind not giving scoped_ptr a custom deleter? Is it that shared_ptr's overhead is negligible (when not being shared I mean)? thanks

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Boost.Serialization problems in VC 7.1
by James Trotter 04 Jan '05

04 Jan '05

Hi, I'm trying to get the boost.serialization library to work, but I'm having some problems. I'm running VC 7.1, and I've tried both boost 1.32, and the latest CVS. I manage to compile and install the library, but when I try to compile and run the demo application that comes with it, I get a runtime error. It's compiling and linking perfectly, but at runtime I get a message box saying: "Unhandled exception at 0x7c59bbf3 in Test.exe: Microsoft C++ exception: __non_rtti_object @ 0x0012f8b0." Anyone had a problem like this before? Anyone know how to fix it?

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thread::thread() in Windows
by Yuval Ronen 04 Jan '05

04 Jan '05

Hi. I believe that there is a bug in thread::thread() under Windows. The code uses GetCurrentThread() WinAPI function, but this is not enough. If you'll try to create such a thread object, and pass its reference to another thread which will join it - something like struct SomeThread { thread *m_thread; SomeThread(thread *a_thread) : m_thread(a_thread) { } void operator()() { do_some_work() m_thread->join(); delete m_thread; } }; { ...somewhere in the code... SomeThread st(new thread()); thread other_thread(st); } then it won't work. The following is a quote from MSDN about GetCurrentThread(): "The return value is a pseudo handle for the current thread... A pseudo handle is a special constant that is interpreted as the current thread handle... The function cannot be used by one thread to create a handle that can be used by other threads to refer to the first thread. The handle is always interpreted as referring to the thread that is using it. A thread can create a "real" handle to itself that can be used by other threads, or inherited by other processes, by specifying the pseudo handle as the source handle in a call to the DuplicateHandle function." The conclusion is that a call to DuplicateHandle() is needed after GetCurrentThread(). Thanks, Yuval

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[MPL] map question
by David Greene 04 Jan '05

04 Jan '05

I'm not understanding something about the interaction of map with the algorithms. I've got a map whose value_type is another map. I'd like to iterate through the map entries and add all the "sub-map" entries to the "primary" map. I wrote a little testcase, attached below. When I compile it with g++ 3.3.3, I get this: boost-1_32/boost/mpl/pair.hpp: In instantiation of `boost::mpl::second<mpl_::_2>': fold2.cc:23: instantiated from `boost::mpl::value_type_impl<boost::mpl::aux::map_tag>::apply<map_types, mpl_::_2>' fold2.cc:23: instantiated from `boost::mpl::value_type<map_types, mpl_::_2>' fold2.cc:23: instantiated from here boost-1_32/boost/mpl/pair.hpp:56: error: no type named `second' in `struct mpl_::_2' fold2.cc:23: error: `types' is not a member of type ` boost::mpl::value_type<map_types, mpl_::_2>' fold2.cc:24: error: template argument 1 is invalid fold2.cc:24: error: ISO C++ forbids declaration of `type name' with no type boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp: In instantiation of `boost::mpl::apply_wrap2<int, map_types, boost::mpl::pair<key1, entry> >': boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp:49: instantiated from `boost::mpl::apply2<int, map_types, boost::mpl::pair<key1, entry> >' boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp:49: instantiated from `boost::mpl::aux::fold_impl<1, boost::mpl::m_iter<map_types, 2, 3>, boost::mpl::m_iter<map_types, 3, 3>, map_types, int>' boost-1_32/boost/mpl/fold.hpp:39: instantiated from `boost::mpl::fold<map_types, map_types, int>' fold2.cc:24: instantiated from here boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp:49: error: ` int' is not a class, struct, or union type boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp: In instantiation of `boost::mpl::aux::fold_impl<1, boost::mpl::m_iter<map_types, 2, 3>, boost::mpl::m_iter<map_types, 3, 3>, map_types, int>': boost-1_32/boost/mpl/fold.hpp:39: instantiated from `boost::mpl::fold<map_types, map_types, int>' fold2.cc:24: instantiated from here boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp:49: error: no type named `type' in `struct boost::mpl::apply2<int, map_types, boost::mpl::pair<key1, entry> >' boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp: In instantiation of `boost::mpl::aux::fold_impl<1, boost::mpl::m_iter<map_types, 2, 3>, boost::mpl::m_iter<map_types, 3, 3>, map_types, int>': boost-1_32/boost/mpl/fold.hpp:39: instantiated from `boost::mpl::fold<map_types, map_types, int>' fold2.cc:24: instantiated from here boost-1_32/boost/mpl/aux_/preprocessed/gcc/fold_impl.hpp:53: error: no type named `type' in `struct boost::mpl::apply2<int, map_types, boost::mpl::pair<key1, entry> >' boost-1_32/boost/mpl/fold.hpp: In instantiation of `boost::mpl::fold<map_types, map_types, int>': fold2.cc:24: instantiated from here boost-1_32/boost/mpl/fold.hpp:39: error: no type named `state' in `struct boost::mpl::aux::fold_impl<1, boost::mpl::m_iter<map_types, 2, 3>, boost::mpl::m_iter<map_types, 3, 3>, map_types, int>' fold2.cc:24: error: syntax error before `;' token fold2.cc:26: error: syntax error before `::' token An EDG-based compiler gives much the same error. What am I doing wrong? Much thanks for the help! -Dave #include <boost/mpl/fold.hpp> #include <boost/mpl/placeholders.hpp> #include <boost/mpl/copy.hpp> #include <boost/mpl/map.hpp> #include <boost/mpl/value_type.hpp> #include <boost/mpl/inserter.hpp> #include <boost/mpl/insert.hpp> #include <boost/mpl/pair.hpp> using namespace boost; using namespace boost::mpl; struct key1 {}; struct key2 {}; struct entry { typedef map<pair<key2, int> > types; }; typedef map<pair<key1, entry> > map_types; typedef fold<map_types, map_types, copy<value_type<map_types, _2>::types, inserter<_1, insert<_1, _2> > > >::type result; result::blah; // Get a printout

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