September 2008 - Boost-users - lists.preview.boost.org

question about boost::thread
by PingShan Li 15 Sep '08

15 Sep '08

Here is my test program using boost::thread. I would expect this program to crash inside FunctionA because m_ClassA is no longer available. Can anybody help me to understand why it does not crash? thank you. [root@localhost]# uname -a Linux localhost.localdomain 2.6.9-22.EL #1 Mon Sep 19 18:20:28 EDT 2005 i686 i686 i386 GNU/Linux [root@localhost]# g++ --version g++ (GCC) 3.4.4 20050721 (Red Hat 3.4.4-2) Copyright (C) 2004 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. g++ -I/opt/third_party_libraries/boost_1_33_1 -L/opt/third_party_libraries/boost_1_33_1/stage/lib -lboost_thread-gcc-mt main.cpp -o test #include <boost/bind.hpp> #include <boost/thread.hpp> #include <iostream> void SleepTime( int a ) { boost::xtime xt; boost::xtime_get( &xt, boost::TIME_UTC ); xt.sec += a; boost::thread::sleep( xt ); } class ClassA { public: ClassA( int member ) : m_member( member ) { std::cout << "ClassA constructor: " << m_member << std::endl; } virtual ~ClassA( ) { std::cout << "ClassA destructor: " << m_member << std::endl; } void SetMember( int a ) { m_member = a; } int GetMember() const { return m_member; } private: int m_member; }; class TestClass { public: TestClass( ) : m_ClassA( 0 ) { std::cout << "TestClass constructor: " << m_ClassA.GetMember() << std::endl; } virtual ~TestClass( ) { std::cout << "TestClass destructor: " << m_ClassA.GetMember() << std::endl; } void RunThreadFunction() { std::cout << "RunThreadFunction start" << std::endl; boost::thread thr( boost::bind( &TestClass::ThreadFunction, this ) ); std::cout << "RunThreadFunction end" << std::endl; } void ThreadFunction( ) { std::cout << "ThreadFunction start" << std::endl; m_ClassA.SetMember( 5 ); SleepTime( 5 ); FunctionA( ); return; } void FunctionA( ) { std::cout << "Inside FunctionA: " << m_ClassA.GetMember() << std::endl; } private: ClassA m_ClassA; }; int main() { { TestClass a; a.RunThreadFunction(); } std::cout << "main wait" << std::endl; SleepTime( 10 ); return 0; }

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[review] FSM Library review result
by Martin Vuille 15 Sep '08

15 Sep '08

This is a summary of the comments received during the review of Andrey Semashev's Finite State Machines (FSM) library. Apologies for the delay in getting these out. DOCUMENTATION * Relocate ToC to make it stand out. * Several people used the Wikipedia article http://en.wikipedia.org/wiki/Finite_state_machine as a reference for FSM terminology and operation, and found discrepancies between Boost.FSM and that description. Perhaps Boost.FSM should explicitly describe its FSM metamodel, or refer to an existing metamodel (Wikipedia FSM or Harel or UML Statechart, for example). The latter was mentioned several times as being preferred since it is a standard. * If possible, use standard terminology. For example, "transition map" vs. "state transition table". Or define the non-standard terms. * Include a comprehensive rationale mapping the design choices to the design objectives. * Compare/contrast Boost.FSM with the FSM implementation as described in "C++ Template Metaprogramming". * Add an example of event deferral using boost::function. * Clarify support for multithreading vs. asynchronous FSM, as some were confused by existing text. * Clarify lifetime of objects. * Add implementation of example using transition map/STT. * Add more complex example(s). SCOPE/FEATURES These were features that were suggested or asked about. Some or all may not be suited for addition to the library. In that event, it may be useful to explicitly mention in the documentation that they are not supported, and why. * Support nested states. Return-to-history was cited as an example of a benefit of nested states over nested FSM. * In STT, support matching "any" from state. * Add syntactic sugar to support "synthetic" states (cf. http://lists.boost.org/Archives/boost/2008/08/140714.php) * Support event deferral. * Support data-dependent transitions (perhaps this is the same as the synthetic state suggestion above). * Improve modeling of the "transition" concept. Specifically, there was an issue with the fact that the action was associated with a state rather than a transition. INTERFACE * There was a lot of discussion comparing the amount of code required to implement an "ad hoc" FSM, vs. the amount of code required to implement the same FSM using Boost.FSM. * The "transition map" representation was deemed to contain too much syntactic noise and not sufficiently similar to a traditional STT, and it was suggested that it should include the transition action. * Some felt that the interface was too procedural rather than being declarative. IMPLEMENTATION * There was quite a bit of discussion of the Boost.FSM implementation vs. the C++TM implementation, but I don't believe there were any specific conclusions reached. * Handling of event is different depending on whether or not transition map is used (handled by "to" state vs. current state, respectively). This is also the case when an event is not found in the transition map. This could lead to errors. Thanks again to Andrey for his submission and to all the reviewers and other who made comments for their input. MV

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[serialization] broken in 1.36
by gast128 15 Sep '08

15 Sep '08

Dear all, yesterday we upgraded to vstudio 2008 and Boost 1.36. However it seems that the serialization library gives a STATIC_WARNING now. the code uses a shared_ptr of a data structure which has no virtual function. This was ok in Boost 1.34 and I don't see why this should be wrong: #include "stdafx.h" #include <sstream> #include <boost\shared_ptr.hpp> #include <boost\serialization\shared_ptr.hpp> #include <boost\serialization\nvp.hpp> #include <boost\archive\xml_iarchive.hpp> struct Data { std::string m_str; }; template <class Archive> void serialize(Archive& ar, Data& r, const unsigned int /*version*/) { ar & BOOST_SERIALIZATION_NVP(r.m_str); } struct DataStorage { template <class Archive> void serialize(Archive& ar, const unsigned int /*version*/) { ar & BOOST_SERIALIZATION_NVP(m_ptrBla); } private: //data typedef boost::shared_ptr<Data> DataPtr; DataPtr m_ptrBla; }; int _tmain() { DataStorage data; std::stringstream sstr; //boost::archive::xml_oarchive oa(sstr); //oa << boost::serialization::make_nvp("bla", data); boost::archive::xml_iarchive ia(sstr); ia >> boost::serialization::make_nvp("bla", data); return 0; } It gives warning c4099 where '<---': const extended_type_info * get_derived_extended_type_info(const T & t) const { // note: this implementation - based on usage of typeid (rtti) // only does something if the class has at least one virtual function. BOOST_STATIC_WARNING(boost::is_polymorphic<T>::value); //<--- return detail::extended_type_info_typeid_0::get_extended_type_info( typeid(t) );

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[shared_ptr] why isn't null_deleter included into smart_ptr lib
by Ovanes Markarian 15 Sep '08

15 Sep '08

Hi all! I am wondering, why null_deleter which is sugested in the programming techniques web site of shared_ptr library not a part of utility lib or smart_ptr lib. In the past I worked in at least 3 projects where people defined there own null_deleter. Best Regards, Ovanes

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Problems with boost::asio::local::stream_protocol::iostream under Boost 1.36.0
by Jason Bertschi 15 Sep '08

15 Sep '08

I'm trying to use asio::local::stream_protocol::iostream to connect to a server (using Boost library version 1.36.0). The code looks something like this: boost::asio::local::stream_protocol::iostream mgmtStream("/tmp/pipes/mgmtsock"); if (!mgmtStream) throw std::exception(); // Send cmd to mgmt mgmtStream << cmd << std::flush; I get a compilation error on the line creating mgmtStream. The interesting part is this: no type named 'resolver_query' in 'class boost::asio::local::stream_protocol' I tried breaking the creation into two steps (create local::stream_protocol::endpoint with the name of the socket then passing the endpoint into the iostream constructor), but the result was about the same (the failure occurred on the line creating the iostream, not the line creating the endpoint). The problem seems to be that basic_socket_streambuf<stream_protocol> requires the definition of type resolver_query (within stream_protocol in this case). It seems that ip::tcp::iostream declares it to be of type ip::basic_resolver_query<tcp>; I saw no obvious equivalent in the local namespace, and my attempt to add 'typedef ip::basic_resolver_query<stream_protocol> resolver_query;' to stream_protocol of course did nothing helpful (just added a lot more compilation errors). Frankly, I'm not sure how stream_protocol::iostream could possibly compile without this definition somewhere... Any ideas? Below is the full output from g++ (in case there's something helpful): export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp: In instantiation of 'boost::asio::basic_socket_streambuf<boost::asio::local::stream_protocol, boost::asio::stream_socket_service<boost::asio::local::stream_protocol> >': export_Darwin_i386/include/boost/utility/base_from_member.hpp:69: instantiated from 'boost::base_from_member<boost::asio::basic_socket_streambuf<boost::asio::local::stream_protocol, boost::asio::stream_socket_service<boost::asio::local::stream_protocol> >, 0>' export_Darwin_i386/include/boost/asio/basic_socket_iostream.hpp:86: instantiated from 'boost::asio::basic_socket_iostream<boost::asio::local::stream_protocol, boost::asio::stream_socket_service<boost::asio::local::stream_protocol> >' build_Darwin_i386/confdb/ObjectManager.cc:461: instantiated from here export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp:252: error: no type named 'resolver_query' in 'class boost::asio::local::stream_protocol' export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp: In member function 'boost::asio::basic_socket_streambuf<Protocol, StreamSocketService>* boost::asio::basic_socket_streambuf<Protocol, StreamSocketService>::connect(T0) [with T0 = const char*, Protocol = boost::asio::local::stream_protocol, StreamSocketService = boost::asio::stream_socket_service<boost::asio::local::stream_protocol>]': export_Darwin_i386/include/boost/asio/basic_socket_iostream.hpp:106: instantiated from 'boost::asio::basic_socket_iostream<Protocol, StreamSocketService>::basic_socket_iostream(T0) [with T0 = const char*, Protocol = boost::asio::local::stream_protocol, StreamSocketService = boost::asio::stream_socket_service<boost::asio::local::stream_protocol>]' build_Darwin_i386/confdb/ObjectManager.cc:461: instantiated from here export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp:131: error: no type named 'resolver_query' in 'class boost::asio::local::stream_protocol' export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp:131: error: no type named 'resolver_query' in 'class boost::asio::local::stream_protocol' export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp:131: error: no type named 'resolver_query' in 'class boost::asio::local::stream_protocol' export_Darwin_i386/include/boost/asio/basic_socket_streambuf.hpp:131: error: 'resolve_and_connect' was not declared in this scope Thanks, Jason Bertschi jbertschi(a)mac.com

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[multi_index_container] Usage Idioms
by Robert Jones 15 Sep '08

15 Sep '08

My head is now exploding with understanding the full power and flexibility of multi-index-container, but still it is not clear to me how best to do the simple things! What is the idiomatically 'correct' way to apply the equivalent functionality of the erase-remove idiom to a multi-index-container? I'm assuming that this, (very much abridged for brevity of exposition) multi_index_container mic; mic.erase( remove_if( mic.begin(), mic.end(), pred ), mic.end() ); is doomed since the remove algorithms overwrite removed elements with copied elements which would cause havoc with other indices, and in any case this kind of modification through iterators is explicitly prohibited. I did think of extracting a vector of references, doing erase-remove on that and then applying rearrange(), but it seems rather inelegant. Is there a better way? Thanks. - Rob.

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Documentation about design and implementation
by Kartik Mahajan 15 Sep '08

15 Sep '08

Hi I have recently installed Boost 1.36. I am right now experimenting with the Boost.thread library primarily for the purpose of learning and I am trying to use them in the project I am working. I also wish to learn to use asio and interprocess libraries in near future. I have gone through the documentation about how to use the thread library, but I guess there is nothing mentioned about its design and implementation. The only reason I am interested in some documentation related to its design and implementation is purely for learning purpose. As Boost libraries are designed mostly by experts, I would like to broaden my horizons "on how to design". I would not like to be just a user of such expertly designed libraries and would like to learn the ins of designing. Also going through the code would I guess improve my skills. I did read some include files and also installed cscope on my linux box so that I can go through code easily but its too hard for me to comprehend why the things ie code is written the way it is. Is some documentation related to implementation of the library available ? I guess no ? Do we just have to comprehend by reading the code ? Are there some tips for reading the code ( I am even unable to find which file to start from, I am still a newbie ) I just need some tips and guidance. Thanks & Regards Kartik Mahajan

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IoStreams: Weird bzip2 behavior?
by Dr. Roland Bock 15 Sep '08

15 Sep '08

Hi, when experimenting with IoStreams a bit, I tried bzip2 compression, too. In contrast to zlib and gzip compression, it did not work as expected. I have a bit weird behavior in two aspects. a) Unknown error code: ====================== The attached code yields: Caught bzip2 error with code: -2 data_error: -4 data_error_magic: -5 config_error: -9 So for some reason, I am catching a bzip2_error with an error code which is not even documented. When I replace gzip2 by zlib, it works fine. b) Empty output of compression: =============================== When I use a std::ofstream instead of the decompressingStream, I get an empty file. This might be the reason for a), but then I would have expected data_error or data_error_magic? Decompressing the content of a valid bzip2 compressed file works fine. Any ideas what might be going wrong? Thanks in advance, Roland

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[Boost][Serialization] CPU bottleneck
by Vjekoslav Brajkovic 14 Sep '08

14 Sep '08

Hi, I am using the serialization library in my project and it has been functioning perfectly thus far. However, when I've scaled up the usage requirements, I had hit a very odd problem. Let me explain the use case. Serialization library is used in a DFS framework, handling large data structures (in terms of size, not complexity) such as std::vector<char> of size 1MB and above. The framework consists of two major components: Chunkserver (server) and a Client. Files are chunked, wrapped in a class, serialized and sent over the wire. Same things is done on the server side, but in a reverse order. The actual binary data is stored in a vector (previously, I've tried using string instead, but I had some issues with it and Robert suggested using some an alternative container). When I was depositing large files to Chunkserver, disk utilization was almost non-existent, whereas the CPU was maxed out. It is important to realize that this problem occurred only on the server side, not client. Upon further investigation using gprof I have concluded that the bottleneck was in the serialization library (it also may be the case that I am misusing it). According to the profiler, above 97% of the CPU time was spent in a singe function. Profiler results can be found at this address: http://www.cs.washington.edu/homes/balkan/gprof.txt For the reference, the signature of that function is: boost::serialization::serialize_adl< boost::archive::text_iarchive, std::vector...> and I am using text archive. I as mentioned before, this issue only occurs on a server side. I would appreciate if anybody could explain why this is happening and more importantly how to circumvent the issue. Thank you! Vjeko

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What's the status of unordered_map.hpp?
by Peng Yu 14 Sep '08

14 Sep '08

Hi, In http://www.boost.org/doc/libs/1_35_0/doc/html/boost_tr1/unsupported.html, it shows the header file is <boost/tr1/unordered_set.hpp> for unordered_set. But I only find the following two files in version 1.36.0. boost/unordered_map.hpp I'm wondering if unordered_map is not stable yet, so that I'd better avoid using it. Or it will be stable from version 1.36.0 on? Thanks, Peng

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