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BGL: Vertex or Vertex& ?
by Roger House 30 Jan '09

30 Jan '09

I've just started using the Boost Graph Library (which is proving to be a very nice tool) and I've encountered an issue: When vertex descriptors are passed as parameters, stored in vectors, etc., is it better to use Vertex&, or is Vertex alone okay. I've been assuming that a vertex descriptor is probably a pointer, so I've been using Vertex. But then is occurred to me that my assumption could be all wrong and I should be using Vertex&. Here are the Graph, Vertex, and Edge definitions I've been using: typedef adjacency_list < vecS, // edge container type vecS, // vertex container type undirectedS, VertexProperties, EdgeProperties, GraphProperties > Graph; typedef graph_traits<Graph>::vertex_descriptor Vertex; typedef graph_traits<Graph>::edge_descriptor Edge; Roger House

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David M Garza is out of the office.
by David M Garza 30 Jan '09

30 Jan '09

I will be out of the office starting 01/30/2009 and will not return until 02/03/2009. I will respond to your message when I return.

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[ASIO] random crashes
by Axel 30 Jan '09

30 Jan '09

Hello I m using ASIO library (from boost 1.35) in a network daemon (running on a Debian Etch system). The code structure is almost the same as the one described in the HTTP Server example (http://tenermerx.com/Asio/boost_asio_1_3_1/doc/html/boost_asio/examples.htm…) One io_service is used, async_accept() creates new "sessions" and so on. The daemon can run flawlessly for weeks (or only some hours), and crash randomly (segmentation fault). The "network" load isn't really high, every 5 minutes, a few megabytes of data (characters) are sent to the daemon. I didn't noticed any memory leaks or null pointers accesses. Among many crashes, I found 2 kind of crashes. Since core are dumped, I tried to debug it, but I don't know how to interpret the core result. The binary wasn't linked against debug libraries and I just can get debug data from the binary itself. Here's the gdb output on "bt full" command. The daemon has 4 threads, here s the gdb output of the one which causes the crash (I assume this is this one) First kind of crash : (only the relevant part is pasted, the output is huge). It seems to be related to the way I handle the timeout on a timer. In my daemon, the io_service thread may call close() function on the socket object when another thread may call cancel() on the socket object. Could this lead to a crash ? (I can post source code if needed) What is the best way to handle receive timeout *and* socket & timer close from another thread ? Thread 1 (process 27120): Program terminated with signal 11, Segmentation fault. #0 0xb7c7c024 in pthread_mutex_lock () from /lib/tls/i686/cmov/libpthread.so.0 No symbol table info available. #1 0xb7d5f0c6 in pthread_mutex_lock () from /lib/tls/i686/cmov/libc.so.6 No symbol table info available. #2 0x08060438 in boost::asio::detail::posix_mutex::lock (this=0x16) at /usr/include/boost/asio/detail/posix_mutex.hpp:71 error = 0 #3 0x08060559 in scoped_lock (this=0xb796807c, m=@0x16) at /usr/include/boost/asio/detail/scoped_lock.hpp:36 No locals. #4 0x08060ad0 in boost::asio::detail::epoll_reactor<false>::close_descriptor (this=0x2, descriptor=-1291829448) at /usr/include/boost/asio/detail/epoll_reactor.hpp:297 lock = {<boost::noncopyable_::noncopyable> = {<No data fields>}, mutex_ = @0x16, locked_ = 212} ev = {events = 6, data = {ptr = 0x25, fd = 37, u32 = 37, u64 = 8589934629}} #5 0x0809b189 in boost::asio::detail::reactive_socket_service<boost::asio::ip::tcp, boost::asio::detail::epoll_reactor<false> >::close (this=0xb3004358, impl=@0xb3037f1c, ec=@0xb7968128) at /usr/include/boost/asio/detail/reactive_socket_service.hpp:210 No locals. #6 0x0809b277 in boost::asio::stream_socket_service<boost::asio::ip::tcp>::close (this=0xb3000098, impl=@0xb3037f1c, ec=@0xb7968128) at /usr/include/boost/asio/stream_socket_service.hpp:145 No locals. #7 0x0809b2c5 in boost::asio::basic_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >::close (this=0xb3037f18) at /usr/include/boost/asio/basic_socket.hpp:253 ec = {m_val = 0, m_cat = 0xb7c74c10} #8 0x08091129 in Session::handleTimeout (this=0xb3037f18, error=@0xb796821c) at Session.cc:80 Could someone bring me some explainations about this crash ? Second kind of crash : (I really have no idea from where could come the crash, the backtrace isn't very useful) (gdb) bt full #0 boost::asio::detail::scoped_lock<boost::asio::detail::posix_mutex>::unlock (this=0xb5631dac) at /usr/include/boost/asio/detail/scoped_lock.hpp:58 No locals. #1 0x00000000 in ?? () No symbol table info available. Could someone give me some advices about how to handle these crashes ? How could I get more data in backtrace ? Thanks in advance for your help. Regards

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seg fault on windows with Boost threads, istringstream, mingw
by Tod Courtney 30 Jan '09

30 Jan '09

Hi I am working on a multithreaded application for linux and windows using Boost threads. For windows, we have been developing with MinGW G++ 3.4.4 (packaged in cygwin). My application uses a producer-consumer model where one thread produces tasks definitions and multiple worker threads complete the tasks. I discovered that our application runs fine on linux but crashes with a SIGSEGV fault on windows, at least when compiled with MinGW. When compiling the same application with MSVC it works fine. The SIGSEGV crash is not always in the exact same place in the code, but is very likely to occur -- it happens 99% of the time when there are 3 or more worker threads. The code runs fine if there is only 1 worker thread. If I try to use the debugger to get a stack trace, I find the stack is corrupted so I can not see the method or source code lines that caused the crash. I have tried boost 1.36 and 1.37. I have tried MinGW g++ 3.4.4 (from cygwin), 3.4.5 (main release) and 4.3 (alpha). I get the same results in all cases. I have added the -mthreads flag to the compile and link options for my application. I believe the problem is related to this code, which uses a istringstream to convert a string to a basic type (say a double): template <typename T> bool FromString(T &t,const std::string &s, std::ios_base &(*f)(std::ios_base &)=std::dec) { std::istringstream iss(s); return !(iss >> f >> t).fail(); } The istringstream object is local to the conversion function, and each istringstream is unique for each thread. So I wouldn't expect a thread-related problem, unless istringstream has internal state stored in static variables. However, if I replace that code with equivalent calls to C-lib functions like 'atof', the problem goes away. I have attached a test application, along with the makefile I use to build it, that demonstrates this problem. This test application fails for with a SIGSEGV when run with MinGW GCC 3.4.4 (from cygwin), MinGW 3.4.5 (current MinGW release) or MinGW GCC 4.3 alpha. It works fine when I compile with MSVC or Cygwin GCC (non-mingw version based on cygwin1.dll and pthreads). I hope there is a solution but at this point and hope for some help answering these questions: 1) Is there a multi-thread bug in the MinGW implementation istringstream? 2) Is there a problem with my build process? Am I missing a flag or using the wrong variation of a library? 3) Is this problem unique to my machine or reproducible by others? 4) Has anyone else encountered a similar issue? If you have experience with using Boost threads with MinGW I would love to hear any pointers or suggestions you can share. If you try this test application with MinGW G++ and it works I would love to know it. If multiple people can confirm this is a bug, I want to submit it to either the MinGW or Boost threads dev. teams. Thanks in advance for your help, Tod Courtney -- Tod Courtney Delcross Technologies LLC tcourtney(a)delcross.com, www.delcross.com (217) 363-3396 ext 103 mingw34: test.cpp c:\\MinGW\\bin\\g++ -mthreads -o mingw34 test.cpp -I c:\\boost\\boost_1_37_0 -L c:\\boost\\boost_1_37_0\\stage\lib -lboost_thread-mgw34-mt newmingw43: test.cpp c:\\mingw4\\bin\\g++ -mthreads -o newmingw43 test.cpp -I c:\\boost\\boost_1_37_0 -L c:\\boost\\boost_1_37_0\\stage\\lib -lboost_thread-mgw43-mt nocygwin: test.cpp /usr/bin/g++ -mthreads -o nocygwin test.cpp -I /cygdrive/c/boost/boost_1_37_0 -L /cygdrive/c/boost/boost_1_37_0/stage/lib -mno-cygwin -lboost_thread-mgw34-mt cygwin: test.cpp /usr/bin/g++ -o cygwin test.cpp -I /cygdrive/c/boost/boost_1_37_0 -L /cygdrive/c/boost/boost_1_37_0/stage/lib -lboost_thread_pthread-gcc34-mt-1_37 #include <string> #include <vector> #include "boost/bind.hpp" #include "boost/thread.hpp" #include "boost/thread/barrier.hpp" using namespace std; boost::mutex msgMutex; //////////////////////////////////////////////////////////////////////// /// threadsafe tracing method void msg(const std::string &str) { boost::mutex::scoped_lock lock(msgMutex); cout<<str<<endl; } //////////////////////////////////////////////////////////////////////// /// method run by each worker thread bool exec(std::vector<string> * vec) { char buff[256]; // wait here until all threads have been created msg(string("START THREAD: ")); // now do the work for(size_t n=0;n<vec->size();n++) { string val=(*vec)[n]; double d=0; d=atof(val.c_str()); // COMMENTING OUT THE NEXT TWO LINES AVOIDS THE SIGSEGV istringstream iss(val); iss>>d; sprintf(buff,"value=%lf",d); msg(string(buff)); } msg("EXEC DONE: "); return true; } //////////////////////////////////////////////////////////////////////// /// main method: parse inputs and create worker threads int main(int argc, char **argv) { int numThreads=0; if (argc==2) numThreads=atoi(argv[1]); else cout<<"USAGE: "<<argv[0]<<" <numthreads>"<<endl; boost::thread **worker; vector<string> **vec; worker=new boost::thread*[numThreads]; vec=new vector<string>*[numThreads]; for(int n=0;n<numThreads;n++) { vec[n]=new vector<string>; for(int m=0;m<10;m++) { ostringstream oss; oss<<n<<"."<<m; vec[n]->push_back(oss.str()); } worker[n]=new boost::thread(boost::bind(&exec,vec[n])); } // wait until all threads to end for(int n=0;n<numThreads;n++) { worker[n]->join(); delete worker[n]; delete vec[n]; } delete [] worker; delete [] vec; }

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[serialization] Can access::destroy (please) be removed?
by Maarten Nieber 30 Jan '09

30 Jan '09

Hi, my compiler (Visual Studio 2003) gives an error in access.hpp when I try to serialize an object that has a protected destructor (see summarized compiler output below). If I comment out the call to delete in access::destroy, the compiler does no longer complain and my code seems to work. Is the destroy function (or: the delete call) really needed? Thanks!, Maarten MyClass::MyClass' : cannot access protected member declared in class 'MyClass' boost\archive\detail\iserializer.hpp(105) : see reference to function template instantiation 'void boost::serialization::access::destroy<T>(const T *)' being compiled

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[boost][asio] deadline_timer doesn't delays - async_wait invokes handler at once
by tomasz jankowski 30 Jan '09

30 Jan '09

Hello, I would like to add timeout to my server which is based on "http server 3" example. But I don't know why but I can't force deadline_timer to work properly. deadline_timer doesn't delays invoking of handler. please look how I modified source code of connection::start() in "http server 3" example. I did it according to suggestion placed on http://lists.boost.org/Archives/boost/2007/04/120339.php Could someone tell me what I.m doing wrong? tom void set_result(boost::optional<boost::system::error_code>* a, boost::system::error_code b) { a->reset(b); } void connection::start() { boost::optional<boost::system::error_code> timer_result; boost::asio::deadline_timer timer(socket_.io_service(),boost::posix_time::seconds(5)); timer.async_wait(boost::bind(set_result, &timer_result, _1)); boost::optional<boost::system::error_code> read_result; socket_.async_read_some(boost::asio::buffer(buffer_), strand_.wrap( boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred))); socket_.io_service().reset(); while (socket_.io_service().run_one()) { if (read_result){ timer.cancel(); }else if(timer_result) { socket_.cancel(); } } if (*read_result) { throw boost::system::system_error(*read_result); } } ---------------------------------------------------- Pierwszy w Polsce profesjonalny serwis o modelkach! Zobacz zdjęcia, video i piękne kobiety. - Kliknij: http://klik.wp.pl/?adr=http%3A%2F%2Fcorto.www.wp.pl%2Fas%2Falemodelki.html&…

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Bug in Ublas' Inner Product between Matrix and Vector?
by Gundala Viswanath 30 Jan '09

30 Jan '09

Hi all, I am trying to perform an inner product multiplication with ublas between this Matrix and Vector: ublas::matrix <double> inputMat (5,5,0); [5,5]((0.994704,0.000882587,0.000882587,0.000882587,0.00264776),(0.00527045,0.989459,0.00263523,0.00263523,0),(0,0,0.00528298,0,0),(0,0,0,1,0),(0,0,0,0,1)) ublas::vector <double> inputVec (5); [5](0.4,0.2,0.2,0.2,0.2) The result I get is this: [5](0.398941,0.201054,0.0010566*,0.2,0.2) Where as the correct one should be (using R): 0.3999707,0.1981258,0.2007013*,0.2007013,0.2005310 Note the significant discrepancy in the 3rd element (*). The product command I use is this: ublas::vector <double> Result (5); Result = ublas::prod(inputMat,inputVec); Is there anything wrong with my way of doing inner product or it is a bug? - Gundala Viswanath Jakarta - Indonesia

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linking boost in a shared library using -fPIC
by jono 30 Jan '09

30 Jan '09

hi. i'm building a shared library under gcc 4.1.1 which links some boost 1.33.1 libraries. a predecessor added the -fPIC switch to the Jamfiles of boost 'thread', 'date_time' and 'regex', and i have had no problems linking them. i've added the boost 'filesystem' library to the project and similarly patched the Jamfile... . . . lib boost_filesystem : ../src/$(SOURCES).cpp : # build requirements <define>BOOST_FILESYSTEM_STATIC_LINK <include>$(BOOST_ROOT) <sysinclude>$(BOOST_ROOT) <no-warn>exception.cpp <no-warn>operations_posix_windows.cpp #******************** <gcc><*><cxxflags>"-fPIC" #******************** # common-variant-tag ensures that the library will # be named according to the rules used by the install # and auto-link features: common-variant-tag : debug release # build variants ; . . . ... and recompiled boost. but i still get the following linker error. ------------------------------------------------------------- gcc-Link-action bin/blablabla/libinterpreter.so/gcc/debug/shared-linkable-true/threading-multi/libinterpreter.so /usr/bin/ld: /home/jono/lib/boost/bin_linux/debug/libboost_filesystem.a(operations_posix_windows.o): relocation R_X86_64_32 against `a local symbol' can not be used when making a shared object; recompile with -fPIC /home/jono/lib/boost/bin_linux/debug/libboost_filesystem.a: could not read symbols: Bad value ------------------------------------------------------------- can anyone spot my deliberate mistake? cheers Jono

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from range_iterator to range_value
by er 29 Jan '09

29 Jan '09

Hello, Is this, or a class that achieves the same goal, already defined somewhere in the boost? template<typename R> struct range_value{ typedef typename iterator_value<typename boost::range_iterator<R0>::type>::type type; }; Thanks.

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[serialization] Support for smart pointers?
by Robert Dailey 29 Jan '09

29 Jan '09

Hi, The documentation for Boost.Serialization states that support for loading/saving pointers is fully supported out of the box. However, what if I want to use smart pointers, such a boost::scoped_ptr? Right now I believe I would have to do this: Foo* foo1; archive & foo1; boost::scoped_ptr<Foo> foo2( foo1 ); I was thinking it would be convenient to avoid the extra variable (foo1) and do this: boost::scoped_ptr<Foo> foo2; archive & foo2; Is this possible?

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