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[ASIO] io_service.run() call is not blocking until async_write completes
by nick aschberger 23 Feb '09

23 Feb '09

Hi Folks, I am using boost 1.36, and I have a C++ class that wraps calls to boost::asio sockets. There are two important functions: WriteData -- takes a vector of uint8_t's and uses async_write. WaitForPreviousWritestoComplete -- Here the user expects to block until all their previous writes are complete. Effectively this just calls io_service.run(). A user of this class can will WriteData a few times, and then do some other processing for a bit while the async_write is happening in the background, and then they should block at io_service.run() until the writes complete (and error status etc is checked). It was my understanding that io_service.run() call would block the thread of execution at that point until the pending writes on my output socket were complete. Am I wrong in my interpretation, because I see the user effectively doing: async_write async_write async_write io_service.run() async_write async_write io_service.run() The first call to io_service.run() correctly calls my message handler 3 times, for the 3 writes. The second call to io_service.run() I expect to see the handler called twice, but it is not called at all! If I get a bit tricky and do something like: async_write async_write async_write while (!all_writes_comple_flag){ io_service.run() } (the handler will set all_writes_comple_flag when all writes are complete :) ) then the code is effectively busy waiting at that point until it is done, but I do see the handler entered when I expect. Is there some timing issue occurring here? Perhaps the thread that is managing the socket stuff not had a chance to register that it has a pending write waiting? Am I misinterpreting what boost means in the documentation by saying the io_service.run() function blocks? If I am, what should I do to wait until all asynchronous writes are complete? thanks Nick

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Boost.multi_index: how to use a member function instead ofoperator<()?
by Joost Kraaijeveld 23 Feb '09

23 Feb '09

Hi, I want to use in index based on a member function that returns a bool if an element is smaller than an other element like operator<. But I cannot find how to do that. e.g. using namespace ::boost; using namespace ::boost::multi_index; class Object{ bool operator<(const Object& rhs) const; bool fn(const Object& rhs) const; } struct FnIndex{}; typedef multi_index_container< Object, indexed_by < ordered_unique< identity< Square > >, // this uses operator<(const Object&) I believe? ordered_unique< tag< FnIndex >, ?????????????? > > > ObjectContainer; If this possible, what should I use in the place of ????????? TIA -- Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 web: www.askesis.nl

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proto user guide e.g.
by Hicham Mouline 23 Feb '09

23 Feb '09

Hi, continuing to work through the user guide boost_1_38_0/doc/html/proto/users_guide.html, I reached the section Retaining POD-ness with BOOST_PROTO_EXTENDS() I fail to compile the following code with intel10: --------------------------CODE----------------------------- #include <iostream> #include <vector> #include <cmath> #include <boost/proto/core.hpp> #include <boost/proto/tags.hpp> #include <boost/proto/context.hpp> #include <boost/proto/domain.hpp> #include <boost/mpl/assert.hpp> using namespace boost; // Define a placeholder type template<int I> struct placeholder {}; // A type to be used as a domain tag (to be defined below) struct calculator_domain; struct calculator_context : proto::callable_context< calculator_context const > { // Values to replace the placeholders std::vector<double> args; // Define the result type of the calculator. // (This makes the calculator_context "callable".) typedef double result_type; // Handle the placeholders: template<int I> double operator()(proto::tag::terminal, placeholder<I>) const { return this->args[I]; } }; // The calculator<> expression wrapper makes expressions // function objects. template< typename Expr> struct calculator { // Use BOOST_PROTO_BASIC_EXTENDS() instead of proto::extends<> to // make this type a Proto expression extension: BOOST_PROTO_BASIC_EXTENDS(Expr, calculator<Expr>, calculator_domain) // Define operator[] to build expression templates: BOOST_PROTO_EXTENDS_SUBSCRIPT() // Define operator= to build expression templates: BOOST_PROTO_EXTENDS_ASSIGN() typedef double result_type; // Hide base_type::operator() by defining our own which // evaluates the calculator expression with a calculator context. result_type operator()( double d1 = 0.0, double d2 = 0.0 ) const { // As defined in the Hello Calculator section. calculator_context ctx; // ctx.args is a vector<double> that holds the values // with which we replace the placeholders (e.g., _1 and _2) // in the expression. ctx.args.push_back( d1 ); // _1 gets the value of d1 ctx.args.push_back( d2 ); // _2 gets the value of d2 return proto::eval(*this, ctx ); // evaluate the expression } }; // Define a calculator domain. Expression within // the calculator domain will be wrapped in the // calculator<> expression wrapper. struct calculator_domain : proto::domain< proto::generator<calculator> > {}; int main() { calculator< proto::terminal< placeholder<0> >::type > const _1 = {{{}}}; calculator< proto::terminal< placeholder<1> >::type > const _2 = {{{}}}; std::cout << ((_1 + _2)(45., 56.)) << std::endl; } -------------------------------- END CODE -------------------------------- The error is: 1>using typeof emulation 1>C:\Program Files (x86)\boost_1_38_0\boost/proto/generate.hpp(153): error: no suitable user-defined conversion from "const boost::proto::exprns_::expr<boost::proto::tag::plus, boost::proto::argsns_::list2<const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<0>>, 0L>> &, const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1>>, 0L>> &>, 2L>" to 1> "calculator<boost::proto::exprns_::expr<boost::proto::tag::plus, boost::proto::argsns_::list2<const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<0>>, 0L>> &, const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1>>, 0L>> &>, 2L>>" exists 1> return Extends<Expr>(expr); 1> ^ 1> detected during: 1> instantiation of "Extends<Expr> boost::proto::generatorns_::generator<Extends>::operator()(const Expr &) const [with Extends=calculator, Expr=boost::proto::exprns_::expr<boost::proto::tag::plus, boost::proto::argsns_::list2<const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<0>>, 0L>> &, const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1>>, 0L>> &>, 2L>]" at 1> line 145 of "C:\Program Files (x86)\boost_1_38_0\boost/proto/operators.hpp" 1> instantiation of "Left::proto_domain::result<void (boost::proto::exprns_::expr<Tag, boost::proto::argsns_::list2<Left &, Right &>, boost::proto::argsns_::list2<Left &, Right &>::arity>)>::type boost::proto::detail::as_expr_if<Tag, Left, Right, Left::proto_is_expr_, Right::proto_is_expr_>::make(Left &, Right &) [with Tag=boost::proto::tag::plus, Left=const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<0>>, 0L>>, 1> Right=const calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1>>, 0L>>]" at line 290 of "C:\Program Files (x86)\boost_1_38_0\boost/proto/operators.hpp" 1> instantiation of "const boost::proto::detail::as_expr_if<boost::proto::tag::plus, const Left, const Right, void, void>::type boost::proto::exprns_::operator+(const Left &, const Right &) [with Left=calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<0>>, 0L>>, Right=calculator<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1>>, 0L>>]" at line 120 of ".\Test4.cpp" 1> 1>compilation aborted for .\Test4.cpp (code 2)

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Re: [Boost-users] proto user guide e.g.
by Hicham Mouline 23 Feb '09

23 Feb '09

I was using the wrong generator for the domain, it was explained later in the user guide. Apologies,

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[Serialization] Error in serialization of a hash map
by Jack Mullen 23 Feb '09

23 Feb '09

Hi, I'm having a bit of trouble while using the serialization library. (Boost v1.35, gcc, Red Hat Linux). I have a class containing a hash_map (key=string, value=shared_ptr to a class containing a deque): HashMapClass{ friend class boost::serialization::access; template <class Archive> void serialize(Archive &ar, const unsigned in t version){ ar & map; } __gun_cxx::hash_map<std::string const, boost::shared_ptr<DequeClass> map; } //create instance HashMapClass hashMap; // fill hashmap ... //perform serialization every hour or something std::ofstream ofs("file.txt"); boost::archive::binary_oarchive oa(ofs); const HashMapClass &map = hashMap; oa << map; The Problem: This works fine for several saves. I can see the file created changing each time the serialization is done. Then after about four or five saves, it seg faults at the place described below. It looks to me like it's having problems iterating over the hash_map. Any advice on how to diagnose or fix this would be appreciated, Many thanks Jack Segfault at: (__gnu_cxx::_Hashtable_const_iterator<std::pair<std::string const, boost::shared_ptr<HashMapClass> >, std::string const, __gnu_cxx::hash<std::string const>, std::_Select1st<std::pair<std string const, boost::shared_ptr<HashMapClass> > >, std::equal_to<std::string const>, std::allocator<boost::shared_ptr<HashMapClass> > >::operator++()+0xe)[0x65a825a] (boost::archive::detail::oserializer<boost::archive::binary_oarchive, __gnu_cxx::hash_map<std::string const, boost::shared_ptr<HashMapClass>, __gnu_cxx::hash<std::string const>, std::equal_to<std::string const>, std::allocator<boost::shared_ptr<HashMapClass> > >::save_object_data(boost::archive::detail::basic_oarchive&, void const*) const+0x1b2)[0x65a90da] (/usr/lib/libboost_serialization-gcc34-mt-1_35.so.1.35.0(boost::archive::detail::basic_oarchive_impl::save_object(boost::archive::detail::basic_oarchive&, void const*, boost::archive::detail::basic_oserializer const&)+0xd1)[0x8497cd] (/usr/lib/libboost_serialization-gcc34-mt-1_35.so.1.35.0(boost::archive::detail::basic_oarchive::save_object(void const*, boost::archive::detail::basic_oserializer const&)+0x23)[0x849213] (boost::archive::detail::oserializer<boost::archive::binary_oarchive, HashMapClass>::save_object_data(boost::archive::detail::basic_oarchive&, void const*) const+0x15c)[0x65a7db4] (/usr/lib/libboost_serialization-gcc34-mt-1_35.so.1.35.0(boost::archive::detail::basic_oarchive_impl::save_object(boost::archive::detail::basic_oarchive&, void const*, boost::archive::detail::basic_oserializer const&)+0xd1)[0x8497cd] (/usr/lib/libboost_serialization-gcc34-mt-1_35.so.1.35.0(boost::archive::detail::basic_oarchive::save_object(void const*, boost::archive::detail::basic_oserializer const&)+0x23)[0x849213]

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Re: [Boost-users] boost::exception - leaking error_info
by Bruce Laing 23 Feb '09

23 Feb '09

> > > Date: Fri, 20 Feb 2009 19:17:55 -0800 > From: Emil Dotchevski <emildotchevski(a)gmail.com> > Subject: Re: [Boost-users] boost::exception - leaking error_info > On Fri, Feb 20, 2009 at 3:00 PM, Bruce Laing > <bruce.laing(a)eng-software.com> wrote: > > This program seems to be leaking boost::exception::error_info objects. > > Is there something missing here? > > > > - Bruce > > > > What platform? Do you have a complete program that shows the problem? > > This test seems to work as expected: > > #include "boost/exception.hpp" > > class > counter > .... > int > main() > { > c=0; > try > { > throw_func(); > } > catch( an_exception & ) > { > assert(c>0); > } > assert(!c); > } > > Emil Dotchevski > Reverge Studios, Inc. > http://www.revergestudios.com/reblog/index.php?n=ReCode > Emil, The platform is vc++ 8, boost 1.37. Since submitting my inquiry to the list, I cut my boost.exception code out into a separate test program that is very similar to the test code you gave in your reply (thanks for that) , but my test program does not leak, so the problem seems to involve some aspect of context from the original surrounding code that I'm not yet able to identify. I'll write back with an update if I can isolate the interaction that triggers the leakage. - Bruce

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How to use noncopyable?
by Yang Zhang 23 Feb '09

23 Feb '09

Hi, I can't figure out how to properly use noncopyable. I'm always getting things like "has a non-virtual destructor" warnings. In fact, compiling noncopyable_test.cpp gives me: $ g++ -Wall -g3 -o noncopyable_test noncopyable_test.cpp -Wextra -Wconversion -Wpointer-arith -Wcast-qual -Wcast-align -Wwrite-strings -Winit-self -Wno-unused-parameter -Wparentheses -Wmissing-format-attribute -Wfloat-equal -Winline -Woverloaded-virtual -Wsign-promo -Wc++0x-compat -Wsynth /opt/armed/include/boost/noncopyable.hpp: In copy constructor ‘<unnamed>::DontTreadOnMe::DontTreadOnMe(const<unnamed>::DontTreadOnMe&)’: /opt/armed/include/boost/noncopyable.hpp:27: error: ‘boost::noncopyable_::noncopyable::noncopyable(const boost::noncopyable_::noncopyable&)’ is private noncopyable_test.cpp:22: error: within this context noncopyable_test.cpp: In function ‘int main()’: noncopyable_test.cpp:32: note: synthesized method ‘<unnamed>::DontTreadOnMe::DontTreadOnMe(const<unnamed>::DontTreadOnMe&)’ first required here /opt/armed/include/boost/noncopyable.hpp: In member function ‘<unnamed>::DontTreadOnMe&<unnamed>::DontTreadOnMe::operator=(const<unnamed>::DontTreadOnMe&)’: /opt/armed/include/boost/noncopyable.hpp:28: error: ‘const boost::noncopyable_::noncopyable& boost::noncopyable_::noncopyable::operator=(const boost::noncopyable_::noncopyable&)’ is private noncopyable_test.cpp:22: error: within this context noncopyable_test.cpp: In function ‘int main()’: noncopyable_test.cpp:33: note: synthesized method ‘<unnamed>::DontTreadOnMe&<unnamed>::DontTreadOnMe::operator=(const<unnamed>::DontTreadOnMe&)’ first required here Any hints? Thanks in advance. -- Yang Zhang http://www.mit.edu/~y_z/

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[Range] Single Pass Range functionality
by Edward Diener 23 Feb '09

23 Feb '09

In the Boost Range documentation describing the Range concepts for a single pass range it lists in the expression semantics post-condition for boost::begin(a): "boost::begin(a) is either dereferenceable or past-the-end. It is past-the-end if and only if boost::distance(a) == 0." However the documentation for single pass range does not list boost::distance as a valid expression nor in the reference section is boost::distance listed as a single pass range function. Is boost::distance a valid function when applied to a single pass range ?

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asio: take back ownership of native descriptor
by Koen Deforche 23 Feb '09

23 Feb '09

Dear all, We have been enjoying using asio alot to build cross-platform networking applications. Just recently, however, we have encountered a limitation that seems impossible to work around, and, would only require a small addition in the API to accomodate. We are trying to add one or more native socket descriptors into asio's reactor to be informed when it is possible to write or read from these descriptors. Therefore, we are creating a tcp::socket and assign() to it a native descriptor. This works, but it seems that nothing can prevent asio from closing the connection in ~tcp::socket() (which does not seem logic since asio did not open the connection in the first place). Should there not be a method to 'take' (back) the descriptor from the asio socket, which resets the socket to the same state as its default constructor ? We tried the workaround that was suggested on the mailinglist, which is to dup() the descriptor. This works on Linux. Unfortunately, dup() is not available on Windows platforms, and when trying to workaround this by using Windows' native methods, we hit the same (so far, unsolved?) problem of this post: http://thread.gmane.org/gmane.comp.lib.boost.user/44269 Regards, koen

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How to implementing a conditional wait
by Daniele Barzotti 23 Feb '09

23 Feb '09

Hi, I have to do a simple task, but I'm quite confused. I have a class that sends some data on RS232 and wait for a answer. (What in Windows is WaitForSingleObject) void ATDispatcher::OnDataReveived() { // Data received from RS232 serial_port.GetData(&buffer); boost::lock_guard<boost::mutex> lock(mut); data_ready = true; cond.notify_one(); }; void ATDispatcher::AtDispatcher(SerialPort& device) : _device(device) { // Connecting the slot for receiving event _device.OnData(boost::bind(&ATDispatcher::OnDataReceived(), &this)); }; int ATDispatcher::SendCommand(std::string cmd, bool waitOK = true, bool decode_answer = true int cmd_timeout = COMMAND_TIMEOUT) { boost::unique_lock<boost::mutex> lock(mut); boost::xtime xt; xtime_get(&xt,boost::TIME_UTC); xt.sec += cmd_timeout; data_ready = false; //Send data.... while(!data_ready) { cond.timed_wait(lock, xt); } }; Ok, The OnDataReceived is called from the SerialPort thread when the data is available. In the SendCommand I have to wait for a timeout or until the answer is arrived...how can I do it? Thanks! Daniele.

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