January 2007 - Boost-users - lists.boost.org

boost::thread - problem with worker as an inner class of a queue
by Lars Kunert 26 Jan '07

26 Jan '07

The following attached (downsized) program implements a queue which contains a single worker process. Int's that are pushed into the queue are popped by the worker and processed... The problem is, the program ends up with an segmentation fault. Valgrind tells me that the stack is overwritten. ==4927== Conditional jump or move depends on uninitialised value(s) ==4927== at 0x8073536: strstr (in /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x80609F5: pthread_initialize (smp.h:47) ==4927== by 0x80B2DE1: (within /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x80480E8: (within /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x80641A0: __libc_csu_init (in /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x8063FC2: __libc_start_main (in /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x8048120: ??? (start.S:102) ==4927== ==4927== Syscall param write(buf) points to uninitialised byte(s) ==4927== at 0x8063044: write (in /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x804C241: boost::thread::thread(boost::function0<void, std::allocator<boost::function_base> > const&) (in /local/home/lkunert/projects/pg-build-4.0.3/src/cdag/threads/queue_error) ==4927== by 0x804AD26: QueueError::QueueError(unsigned) (QueueError.cxx:74) ==4927== by 0x8048287: main (QueueError.cxx:150) ==4927== Address 0x52BFE04C is on thread 1's stack Line 74 corresponds to the initailisation of the worker. The thread-manual writes: *explicit* thread(*const* boost::function0<*void*>& threadfunc); *Effects*: Starts a new thread of execution and constructs a thread <http://www.boost.org/doc/html/thread.html> object representing it. Copies |threadfunc| (which in turn copies the function object wrapped by |threadfunc|) to an internal location which persists for the lifetime of the new thread of execution. Calls |operator()| on the copy of the |threadfunc| function object in the new thread of execution. Which sound good to me. Were is the mistake. class QueueError { // *** Typedefs ************************************************************* private: typedef std::queue<int> Queue; typedef boost::thread Thread; public: typedef Queue::size_type ST; // *** Inner Classes ******************************************************** private: class Worker { private: QueueError* outer_p_; public: Worker( QueueError* outer_p ) : outer_p_( outer_p ) {}; public: void operator()() { outer_p_->worker_run_(); }; }; // *** Attributes ************************************************************ public: private: ST max_queue_size_; Queue queue_; Thread thread_; boost::mutex monitor_; boost::condition space_available_, job_available_; // *** Constructors / Destructors ******************************************** public: explicit QueueError( ST max_queue_size =1000 ) : max_queue_size_( max_queue_size ) , thread_( Worker( this )) {}; // *** Methods *************************************************************** public: void push( int i ) { boost::mutex::scoped_lock lock( monitor_ ); while( queue_.size() >= max_queue_size_ ) { space_available_.wait( lock ); }; queue_.push( i ); job_available_.notify_one(); }; protected: void worker_run_() { int i =0; while( true ) { i = worker_pop_(); worker_work_( i ); }; }; int worker_pop_() { boost::mutex::scoped_lock lock( monitor_ ); while( queue_.empty()) { job_available_.wait( lock ); }; int i = queue_.front(); queue_.pop(); space_available_.notify_one(); return i; }; void worker_work_( int i ) { for( int ii= 0; ii < i; ++ii ) { // do some work double divident = 10000; double sum; for( uint divisor =1; divisor < divident; ++divisor ) { sum = divident / divisor; }; }; }; }; // class QueueError int main() { QueueError q; q.push( 10 ); q.push( 9 ); q.push( 8 ); q.push( 7 ); q.push( 6 ); return 0; };

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problem with boost::strong_components
by Tamas Marki 26 Jan '07

26 Jan '07

Hello, I'm trying to use the boost library's strong_components function to partition a graph to connected sub-partitions, and ran into a problem. Namely, when I generate the graph, for some reason the 'names' (indices) of the vertices have some gaps (basically the graph that needs to be partitioned is generated from another graph by throwing out a bunch of vertices). When I pass this graph to the function, it will count the left out vertices and treat them as 1-vertex sub-partitions, which is not desired. I then tried to use the vertex_index_map named parameter, that I thought would solve this. I used something like this (not the actual code as it would be too big) std::vector<int> other; // fill up the vector with the vertices by pushing back each one. The number of vertices is about 170k and the biggest vertex index is about 260k. // .. // bigedges and bigweights have the edges and the weights, dim is the total number of vertices - all these are checked and proper. graph_t cityg (bigedges.begin (), bigedges.end (), bigweights.begin (), dim); std::vector<int> component(num_vertices(cityg)); int num = strong_components(cityg, &component[0], boost::vertex_index_map (&other[0])); I must be doing it wrong, since it segfaults. The documentation says "This maps each vertex to an integer in the range [0, num_vertices(g))", that's why I thought it would work this way, but it does not. The obvious solution would be to throw out 1-vertex partitions, but I'd really like to know what's the proper way of doing this. Thanks in advance for any help! Tamas

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Link errors with boost regex 1_33_1, Stlport 5.0 and MSVC8
by Manish Mangal 25 Jan '07

25 Jan '07

Hi I have a sample code just to check if I can link to boost regex The code is : #include <boost/regex.hpp> bool testregex( const char* StringToMatch ) { return( boost::regex_match( StringToMatch, boost::regex("[A-Z]+") )); } int main (int argc, char *argv[]) { bool trial = testregex( "hello how r u ?"); return 1; } I am in dll mode both in debug and release versions. The release version compiles, links and runs successfully The debug build, however throws two linker errors: I error LNK2019: unresolved external symbol "public: bool __thiscall boost::re_detail::perl_matcher<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> >,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > >::match(void)" (?match@?$perl_matcher@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd_st d@@U?$regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@re_detail@boos t@@QAE_NXZ) referenced in function "bool __cdecl boost::regex_match<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> >,char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > >(char const *,char const *,class boost::match_results<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> > > &,class boost::basic_regex<char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > > const &,enum boost::regex_constants::_match_flags)" (??$regex_match@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd_std@@DU?$ regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@boost@@YA_NPBD0AAV?$ match_results@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd_std@@@0@ABV ?$basic_regex@DU?$regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@0@ W4_match_flags@regex_constants@0@@Z) 1>Main.obj : error LNK2019: unresolved external symbol "public: __thiscall boost::re_detail::perl_matcher<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> >,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > >::perl_matcher<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> >,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > >(char const *,char const *,class boost::match_results<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> > > &,class boost::basic_regex<char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > > const &,enum boost::regex_constants::_match_flags,char const *)" (??0?$perl_matcher@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd_std@@U ?$regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@re_detail@boost@@Q AE@PBD0AAV?$match_results@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd _std@@@2@ABV?$basic_regex@DU?$regex_traits@DV?$w32_regex_traits@D@boost@ @@boost@@@2@W4_match_flags@regex_constants@2@0@Z) referenced in function "bool __cdecl boost::regex_match<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> >,char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > >(char const *,char const *,class boost::match_results<char const *,class stlpd_std::allocator<struct boost::sub_match<char const *> > > &,class boost::basic_regex<char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > > const &,enum boost::regex_constants::_match_flags)" (??$regex_match@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd_std@@DU?$ regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@boost@@YA_NPBD0AAV?$ match_results@PBDV?$allocator@U?$sub_match@PBD@boost@@@stlpd_std@@@0@ABV ?$basic_regex@DU?$regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@0@ W4_match_flags@regex_constants@0@@Z) Any help is appreciated Manish Mangal Software Engineer atlas(r) search Partner for Results 206-816-8349 // phone Manish.Mangal(a)AtlasSolutions.com <mailto:t-Matt.Koch@AtlasSolutions.com> // email www.AtlasSolutions.com <outbind://116-000000001368D4B5F8F6D0488191444C76FD7C9507008921F4CB773B0 545AAED425DEF553BC300003A3500100000DB0C51F64BED3447AA6EC585072C4EC300000 1E3B7A70000/jenniferh/Local%20Settings/Temporary%20Internet%20Files/OLK3 /www.AtlasSolutions.com> // web

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How can I develop generic test code and using it with the test_suite
by Stephen Torri 25 Jan '07

25 Jan '07

I have the following code for a sample test. I was wondering how I can move code that is common to a long off different test files to a common location and use inheritance? In the code below I can do two things. If its indeed generic I can encapsulate it in a common class used in the tests. Secondly I could put test_one and test_two in a class and inherit from the parent generic class. What is the best solution for what I am trying to do? Stephen ----------CODE-------------- #include <boost/test/unit_test.hpp> #include <fstream> using namespace boost::unit_test; using namespace boost::unit_test_framework; class A {} class B {} A* helper_run_test ( B& target_ref, std::string target_file ) { ... do work on B and return A* result } void test_one () { B& b_ref; A* helper_run_test ( b, "Apple" ); .. perform a BOOST_CHECK_EQUAL } void test_two () { B& b_ref; A* helper_run_test ( b, "Peach" ); .. perform a BOOST_CHECK_EQUAL } test_suite* init_unit_test_suite ( int, char**) { test_suite* test = BOOST_TEST_SUITE ("My test suite"); test->add ( BOOST_TEST_CASE ( &test_one ) ); test->add ( BOOST_TEST_CASE ( &test_two ) ); return test; }

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[type_traits] superfluous add_pointer in function_traits or something else?
by Pavel Antokolsky aka Zigmar 25 Jan '07

25 Jan '07

Hello! I'm trying to use function_traits but it fails to compile. It seems like the add_pointer is somehow related to the error, as using the helper struct directly (and thus avoiding add_pointer on supplied type) compiles ok. I'm using boost 1.30.2 with g++ 3.2.2 on linux. The minimal example is: #include <boost/type_traits/function_traits.hpp> int foo() {} template<typename T> void bar(T f) { typedef typename boost::function_traits<T>::result_type X; //fails to compile typedef typename boost::detail::function_traits_helper<T>::result_type Y; //OK } int main(int argc, char** argv) { bar(foo); } The compiler output is: $ g++ func_traits.cpp func_traits.cpp: In instantiation of `boost::function_traits<int (*)()>': func_traits.cpp:7: instantiated from `void bar(T) [with T = int (*)()]' func_traits.cpp:13: instantiated from here func_traits.cpp:7: base class `boost::detail::function_traits_helper<int (**)()>' has incomplete type func_traits.cpp: In function `void bar(T) [with T = int (*)()]': func_traits.cpp:13: instantiated from here func_traits.cpp:7: no type named `result_type' in `struct boost::function_traits<int (*)()>' Is I'm using function_traits wrong or there is something wrong with the implementation? And another small thing that looks a bit strange to me: for some reason boost/type_traits.hpp does not link boost/type_traits/function_traits.hpp, but it never mentioned in documentation. -- Best regards, Zigmar

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[boost::serialization] want access to binary data sans bookkeeping data
by Brian Stempel 25 Jan '07

25 Jan '07

Hi, I am wanting to serialize some C++ data structures into a binary stream, and I'm wanting to send that binary stream to an embedded python interpreter, where it can unpack the data and make use of it. So, this doesn't seem like a typical use of the serialization library, but I was wondering if it can still work. My problem is that it appears (from what I can tell) that there are various administrative bits inserted by the serialization library into the binary stream, meant for the "unserializer" to make use of in some way (e.g. a header, version information, etc.) Of course, this would mess up things for my python reader. I'd like to, as efficiently as possible, serialize, say, a 3d vector into a binary stream of 3 floats, and then send the raw binary data as an argument to a python function, and have the python function unpack this into 3 floats. This just a simple example though, but as long as the sender (C++) and the receiver (Python) both know the format, I could send arbitrary information this way, as long as there's no other bookkeeping data in the stream. Is there any way to gain access to the raw binary data, after I've filled things with my binary_oarchive, so I can send it to my python function? Or is this just not really a good use of serialization? Thanks!

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[boost-thread] Communication between Threads
by Meryl Silverburgh 25 Jan '07

25 Jan '07

Hi, I notice there is a boost.thread library, but is there a library for inter-threads communication? For example, is there a 'Procedure/Consumer' example for inter-threads communications? Thank you.

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[interprocess] another newbie question: clean-up
by Wolfgang Hottgenroth 24 Jan '07

24 Jan '07

Hi, after I go really quick help here from Ion, I've another question. I managed it to implement a map<string, string> in shared memory and I'm able to put pairs into the map in one process and read them in another process. To put pair into the map I wrote: typedef boost::interprocess::allocator<char, boost::interprocess::managed_shared_memory::segment_manager> ShmemStringAllocator; typedef boost::interprocess::basic_string<char, char_traits<char>, ShmemStringAllocator> MyString; MyString key(segment.get_segment_manager()); MyString value(segment.get_segment_manager()); key = "key1"; value = "value1"; mymap->insert(std::pair<MyString, MyString>(key, value)); (For the complete code see http://www.hottis.de/boost/strings/. Thanks.) What I'm wondering is: will the memory required for key and value be freed automatically in the writing process (put.C)? When I like to erase an element from the map, do I need to do more than just calling mymap->erase(key)? And finally when I'm done and like to remove the whole map, is more required than segment.destroy<MyMap>("MyMap")? Will all the MyString's in the map go too? Furthermore: is it possible to use a map in shared memory as an associative array and write: MyString value = (*mymap)[key]; It doesn't compile for me. Thanks, Wolfgang

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[fusion][mpl::math] generic math operations
by Chris Weed 24 Jan '07

24 Jan '07

Hi, I am interested in combining the fusion and mpl::math libraries, but I am not sure if they currently support what I want to do. I want to use generic math operations that can easily switch between run-time and compile-time. I think this would require writing the mpl::math functions as "Polymorphic Function Object" as described in the fusion documentation. I am not sure if there is any mpl::math documentation that describes this. It looks like the MPL currently has some math operations that are strictly meta-functions in boost/mpl/aux_/arithmetic_op.hpp. Are the any plans to expand these to be functions also? Chris

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code snippet to add line number to lexical_cast exceptions
by bert hubert 24 Jan '07

24 Jan '07

Hi people, I find that I rely on lexical_cast<> a lot, it is a great thing. However, when it throws an exception, and I catch it, I lose information on which of the many lexical_casts had a problem. This is not a lexical_cast specific problem of course, it would be great to have a more general way to add line numbers to exceptions! This led me to code up this small gcc specific hack, but I wonder if there is a better way: #define wrapped_atox(x, y) ({ \ x tmp; \ try { tmp=boost::lexical_cast<x>(y); } \ catch(exception &e) { \ throw std::runtime_error(std::string("On line " + \ boost::lexical_cast<std::string>(__LINE__)+" of " +\ std::string(__PRETTY_FUNCTION__)+" in " +std::string(__FILE__) +\ ", while converting '"+string(y)+"': ") + e.what()); \ } \ tmp; \ }) Which can be used as: cout << wrapped_atox(int, argv[1]) << endl; The code above works, but is gcc specific, and well, it doesn't look right. Perhaps someone has a better idea? Otherwise, people may benefit from the snippet above, feel free to copy it! Bert -- http://www.PowerDNS.com Open source, database driven DNS Software http://netherlabs.nl Open and Closed source services

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