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[boost.signals] documentation suggestion + thread-safe partial implementation
by Frank Hess 26 Jan '07

26 Jan '07

Hi, I'd like to suggest a sentence be added to the boost.signals documentation describing how to connect one signal directly to another signal. It took me a while to realize I could do things like signal.connect(boost::bind(boost::ref(otherSignal), _2)); wrapping a signal object in a boost::ref() call before passing it to boost::bind(), to get around signals being noncopyable. Before this epiphany, I kept writing trivial wrapper functions to use as slots when I wanted to connect two signals :) I imagine others who are new to boost.signals and boost in general would resort to similar tactics. By the way, I hacked up a partial implementation of boost.signals which is intended to be thread-safe, since I missed boost.signals so much in my multi-threaded code. Would anyone would be interested in this? It's just a few header files, and depends on boost (although not on boost.signals). I just did the bare minimum I need for my own use: a signal template class, signalslib::connection, and signalslib::scoped_connection. I didn't implement return values because I don't use them. I didn't implement boost::trackable because I don't see how to make automatic connection management thread-safe when a signal is connected to an object's member function. You really want to insure the slot is disconnected from the signal before the object providing the slot is destroyed. Inheriting the object from boost::trackable wouldn't seem to be good enough, since the boost::trackable destructor wouldn't get called until after the object's destructor. So you pretty much have to manually disconnect the connection at the beginning of the object's destructor. -- Frank

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[interval] using crlibm for transcendental functions
by Tobias Munk 26 Jan '07

26 Jan '07

I am using a custom rounding policy for transcendental functions, based on crlibm and defined in the manner of libs/numeric/interval/examples/transc.cpp In the documentation of crlibm, it is recommended to call the init function crlibm_init() before calling one of their transcendental functions. My question now is: does anybody know if calling this init function collides with any of the boost.numeric.interval internal algorithms? On i686 and amd64 crlibm_init() instructs the FPU not to use extended arithmetics: /* An init function which sets FPU flags when needed */ unsigned long long crlibm_init() { /* Set FPU flags to use double, not double extended, with rounding to nearest */ cw = (_FPU_DEFAULT & ~_FPU_EXTENDED)|_FPU_DOUBLE; _FPU_SETCW(cw); ... } Is it necessary to reset the old state after a call of a crlibm function, for correct interval arithmetics, or is one call of crlibm_init() for the whole program sufficient? Thanks, Tobias Munk --------------------------------- NEU: Fragen stellen - Wissen, Meinungen und Erfahrungen teilen. Jetzt auf Yahoo! Clever.

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regex problem: removing two elements in a row?
by Lynn Allan 26 Jan '07

26 Jan '07

I want to use boost::regex 1.33.1 and vc7.1 on a WinXp-Sp2 computer to remove common words from a file. I'm encountering a problem which seems related to having two of the common words next to each other. std::string test(" in the beginning god created the heavens and the earth "); boost::regex reg; reg.assign("( and | can | did | the | in | a )"); test = boost::regex_replace(test, reg, " "); cout << test << endl; The result is: " the beginning god created heavens the earth " Am I doing something wrong or leaving out a step? Seems like the above ought to work. It catches one of the occurrences of " the " between " created " and " heavens " but not those immediately after the " in " or " and ".

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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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