June 2007 - Boost-users - lists.preview.boost.org

[asio] http-server example
by Daniel Albuschat 13 Jun '07

13 Jun '07

Hello there, I'm currently building my own, specialized http-server based on the http-server example. I experience crashes for certain types of replies. Here's something I really do not understand: In connection.cpp, after request_parser_.parse() finished and result == true, there is this line: boost::asio::async_write(socket_, reply_.to_buffers(), boost::bind(&connection::handle_write, shared_from_this(), boost::asio::placeholders::error)); It's the last user-code in the stacktrace of the crash that I frequently experience. What bothers me is the reply_.to_buffers() function. It looks like this: std::vector<boost::asio::const_buffer> reply::to_buffers() { std::vector<boost::asio::const_buffer> buffers; buffers.push_back(status_strings::to_buffer(status)); for (std::size_t i = 0; i < headers.size(); ++i) { header& h = headers[i]; buffers.push_back(boost::asio::buffer(h.name)); buffers.push_back(boost::asio::buffer(misc_strings::name_value_separator)); buffers.push_back(boost::asio::buffer(h.value)); buffers.push_back(boost::asio::buffer(misc_strings::crlf)); } buffers.push_back(boost::asio::buffer(misc_strings::crlf)); buffers.push_back(boost::asio::buffer(content)); return buffers; } How can this even work? It adds temporaries (the misc_strings are const char[]s) to a const_buffer-vector and reads them later. Even the references to h.name, etc. seem invalid to me, since the io is asynchronous and there's no guarantee that they don't change. IMHO the whole content needs to be COPIED to new buffers and then, after the async_write finished, deleted. Am I missing something? Was the author of this example not aware of the const_buffer's ownership policy (i.e. it is *not* owner of the data)? I've spent hours and hours in debugging now, but I just can't figure out where it goes wrong. You can see the stacktrace here: http://mandrill.fuxx0r.net/c++/paste:7702 Kind regards, Daniel Albuschat -- eat(this); // delicious suicide

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[asio] file streaming
by Chris Fairles 13 Jun '07

13 Jun '07

I give up! I cannot for the life of me figure out buffers and streams. Any help is greatly appreciated. Here's what I have so far: filesize_ = fs::file_size(filepath_); std::ifstream file(filepath_.file_string().c_str(), std::ios::in ); file.seekg (file_offset_, std::ios::beg); //offset typically 0 unless resuming transfer //just trying this for fun boost::asio::ip::tcp::socket::send_buffer_size option; data_socket_.get_option(option); //tcp socket uint64_t size = option.value(); while (bytes_sent < filesize_) { //i test a file 21200678 bytes long. This tranfers anywhere from 21135097 to 21196000. bytes_sent += data_socket_.send(boost::asio::buffer(file.rdbuf(), std::min(size,filesize_-bytes_sent))); //this always transfers 21204202 bytes_sent += data_socket_.send(boost::asio::buffer(file.rdbuf(), size)); } data_socket_.close(); boost::asio::async_read_until(control_socket_, response_, "\r\n", boost::bind(&FTPClient::handleRead, this, boost::asio::placeholders::error)); write_some vs. send give same results. I've also tried something like: char buf[1024]; socket.write_some(buf, file.readsome(buf, 1024)); which deosnt read all the bytes. Sometimes if I check file.rdbuf()->in_avail(), it reports 0 using above method and bytes_sent stops growing about 99% of the way through. I tired setting the the socket linger option to true. No go. I tried making the data_socket a buffered_write_stream, same results. What am I doing wrong? Sometimes bytes_sent is exactly the file size, but the remote file size is slightly less. Maybe closing the socket stream too early? That sends an eof which the server responds to but it should arrive AFTER the data i would think... no clue. please help :) In the meantime, I'm going to go rip up some FSF ftp client code from source forge heh. Thanks Chris

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[iostreams] Using bzip2_decompressor with text files
by Thomas Trummer 13 Jun '07

13 Jun '07

Hi, I have a text file that is compressed with bzip2 and im trying to read with it the iostream lib and parse it with iostream::operator>>. Unfortunately this doesn't work so I wanted to ask if this is an unsupported scenario or if I'm doing something wrong. filtering_istream in; in.push(bzip2_decompressor()); in.push(file_source("text.bz2")); in >> lineId; // std::string lineId Regards, Thomas

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[postmaster@sina.com: boost-users@sina.com??????????]
by Zeljko Vrba 13 Jun '07

13 Jun '07

Enough is enough. I kindly ask the mailing list manager to remove the offending sender(s) (@sina.com) from the mailing list. I attach the complete mail which I get in response to every mail I send to the boost users mailing list. Thanks in advance.

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math/statistics policy-interface feedback requested.
by John Maddock 13 Jun '07

13 Jun '07

Following the successful review of the math-toolkit of special functions and statistical distributions the main feature request was for a better way of customising the library: both for choosing between precision vs speed tradeoffs, and for determining how errors are best handled. I've been experimenting with various policy-based interfaced based on Boost.Parameter, and I think I now have something useable, so I'd like to know what people think: Policy Defaults ~~~~~~~~~~~~~~~ The library will use a sensible set of defaults (throw on domain errors and internal evaluation errors, favour accuracy over speed etc), which can be changed via the usual macro mechanism, so adding: #define BOOST_MATH_DOMAIN_ERROR_POLICY errno_on_error #define BOOST_MATH_OVERFLOW_ERROR_POLICY ignor_error to a user-config header would do what they say to the default policies. Add Hock Changes: ~~~~~~~~~~~~~~~~~ We can create an ad-hock policy change at the call site by using the make_policy function, for example: using namespace boost::math::policy; using namespace boost::math; quantile( poisson(100), 0.05, make_policy( // 5 dicimal digits precision only digits10<10>(), // don't internally promote double->long double for extra precision: promote_double<false>(), // return integer result, immediately below the "real" value: discrete_quantile<integer_below>() )); Which returns the lower 95% quantile (ie critical value) of a poisson distribution with rate parameter of 100 event's per unit time. The result is calculated using only 10 decimal digits internal precision, truncated to the largest integer that gives a CDF less than 0.05. Predefined Policies ~~~~~~~~~~~~~~~~~~~ Although ad-hock policies are useful for testing, I imagine most sites would want a few carefully controlled (and tested) policies. To achieve that you define a typedef of the policy class: using namespace boost::math::policy; typedef policy< // Set error handling: domain_error<throw_on_error>, pole_error<throw_on_error>, overflow_error<throw_on_error>, evaluation_error<throw_on_error>, denorm_error<ignor_error>, underflow_error<ignor_error>, // calculate to 8 decimal digits internally digits10<8>, // don't promote double->long double for accuracy promote_double<false>, // Integer quantiles return the "outside edge": // below the real value for lower critical values, // above it for upper critical values, so that the // area inside contains *at least* the requested coverage: discrete_quantile<integer_outside_edge> > fast_quantile_policy; static fast_quantile_policy fast_quantile; Then we can just use: quantile( poisson(100), 0.05, fast_quantile); In our actual code. Currently this policy interface is vapourware: I have enough of a prototype implemented to know that it's possible to achieve this syntax (this is revision #3 already !), but there's a lot of hairy meta-programming to convert that into something that the library's internals can make use of... so I'd like to know what folks think before I invest too much time messing about with MPL :-) The main disadvantage I've noticed at present, is that the mangled names of the policy class - and therefore all the special functions etc - are *very* long. This has an impact on error messages: in particular we currently use BOOST_CURRENT_FUNCTION to get a nice formatted name of a function that's about to throw, but with function names a couple of pages long I don't think that will be possible with this interface any more :-( Thanks in advance, John Maddock.

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Re: [Boost-users] Boost 1.34 and VC++ 64
by Yutaka Leon Suematsu 13 Jun '07

13 Jun '07

Hi Chris, Thank you for your help. >> The command I used was: >> >> bjam --build-dir=C:\tmp\build-boost --toolset=msvc address-model=64 >> stage > > Hi, > you have to use the 'Visual Studio x64 Win64 Command Prompt', so > the correct environment variables are set and then use bjam like: > > bjam --build-dir=C:\tmp\build-boost --toolset=msvc-8-0_64 stage > I could compile with the toolset "msvc-8.0_64", I didn't know its existence. bjam --build-dir=C:\tmp\build-boost --toolset=msvc-8.0_64 stage Thanks, Yutaka.

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multi_index and base class
by Andrej van der Zee 13 Jun '07

13 Jun '07

Hi, I'm trying to store these classes in a multi_index: struct Foo { int a; }; struct Bar :Foo { }; typedef multi_index_container< Bar, indexed_by< ordered_unique< member<Foo, int, &Bar::a> > > > Bar_container; Notice I have to use "Foo" in the "member<" line. However, even with this, when trying to do a search: Bar_container bar_container; int function() { Bar_container::nth_index<0>::type& a_index = bar_container.get<0>(); Bar_container::nth_index<0>::type::iterator i = a_index.find(5); if (i != a_index.end()) return -1; return 0; } I get this: /usr/include/boost/multi_index/member.hpp: In member function 'Type& boost::multi_index::detail::non_const_member_base<Class, Type, PtrToMember>::operator()(const ChainedPtr&) const [with ChainedPtr = Bar, Class = Foo, Type = int, Type Class::* PtrToMember = &Foo::a]': /usr/include/boost/multi_index/detail/ord_index_ops.hpp:65: instantiated from 'Node* boost::multi_index::detail::ordered_index_find(Node*, const KeyFromValue&, const CompatibleKey&, const CompatibleCompare&) [with Node = boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::i ndex_node_base<Bar> >, KeyFromValue = boost::multi_index::member<Foo, int, &Foo::a>, CompatibleKey = int, CompatibleCompare = std::less<int>]' /usr/include/boost/multi_index/ordered_index.hpp:376: instantiated from 'boost::multi_index::detail::index_iterator<boost::multi_index::detail::orde red_index_node<typename SuperMeta::type::node_type> > boost::multi_index::detail::ordered_index<KeyFromValue, Compare, SuperMeta, TagList, Category>::find(const CompatibleKey&) const [with CompatibleKey = int, KeyFromValue = boost::multi_index::member<Foo, int, &Foo::a>, Compare = std::less<int>, SuperMeta = boost::multi_index::detail::nth_layer<1, Bar, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::mul ti_index::member<Foo, int, &Foo::a>, mpl_::na, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<Bar> >, TagList = boost::mpl::vector0<mpl_::na>, Category = boost::multi_index::detail::ordered_unique_tag]' multitest2.cc:55: instantiated from here /usr/include/boost/multi_index/member.hpp:84: error: no match for 'operator*' in '*x' I've tried a few alternatives such as providing a custom compare function but I always get this error. It seems to have something to do with the fact that the key is in the base class. If I move the key to the derived class (and change the "member<" line), it works fine. Surely there's a way to do this. Anyone know how ? Using gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21) and libboost 1.33.1. Thanks ___________________________________________________________ New Yahoo! Mail is the ultimate force in competitive emailing. Find out more at the Yahoo! Mail Championships. Plus: play games and win prizes. http://uk.rd.yahoo.com/evt=44106/*http://mail.yahoo.net/uk

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Problems instantiating class Boost Python class
by Phil 13 Jun '07

13 Jun '07

Hi, I'm a newbie having some problems instantiating a class written in C++ in Python using Boost.Python. I can get a very simple example working when I expose a function outside of a class, that returns a string, but the below fails as shown, despite building. The enum in the same library however works fine. I've googled the error returned from Python and I get zero hits - has anyone get any idea what I'm doing wrong? I'm using Python 2.5, GCC 4.0.1 and Boost 1.33 on Mac OS X 10.4.9. I don't think it matters but I'm building the solution as a dynamic C++ bsd library in XCode and the changing the Mac OS X .dylib extention to .so as is required by Python. This all works for simpler examples and the enum in this example. Error: TypeError: __init__() should return None, not 'NoneType' Thanks, Phil. From header file example.h: enum payOffType { CALL, PUT }; class Option { public: //defaults to call Option( double strike, double expiry ); double getPutCallMultiplier(); private: double strike; double expiry; payOffType type; }; From cpp file example.cpp: Option::Option( double strike, double expiry ) : strike( strike ), expiry( expiry ), type( CALL ) { cout << "Option Contructor called"; } double Option::getPutCallMultiplier() { return ( type == CALL ) ? 1 : -1; } BOOST_PYTHON_MODULE(libphil_boost) { class_<Option>("Option", init<double, double>()) .def("getPutCallMultiplier", &Option::getPutCallMultiplier) ; enum_<payOffType>("payOffType") .value("CALL", CALL) .value("PUT", PUT) ; } Using Python on the resulting .so: $ python Python 2.5.1 (r251:54863, Jun 10 2007, 17:57:56) [GCC 4.0.1 (Apple Computer, Inc. build 5250)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import libphil_boost >>> p = libphil_boost.Option( 23, 23 ) Option Contructor calledTraceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: __init__() should return None, not 'NoneType' >>>

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boost::pool issue
by v r 12 Jun '07

12 Jun '07

Hi, I have a main object that allocates many small objects via singleton_pool , and during its operation main obj uses up much memory so i want to release that memory before program termination, because main obj performs only support operations in my program. So upon main obj destruction i make a singleton_pool::purge_memory() call in main obj destructor, the memory is released and i should be quite happy,but when the main obj is constructed again the pool allocates twice as much memory as it used before, and it continues to double every time i construct/destruct the main object, so very soon my program hangs up. I wonder what have i done wrong? It seems like something is not reset on memory purge, or maybe it`s a bug? --------------------------------- Вы уже с Yahoo!? Испытайте обновленную и улучшенную Yahoo! Почту!

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[asio] Receiving non-UDP multicast frames?
by Eric Hill 12 Jun '07

12 Jun '07

I have been requested to write a tiny diagnostic application that will listen for Cisco Discovery Protocol (CDP) messages from Cisco switches on a workstation so that the workstation will "know" what switch port it is plugged into. I have found the following information with my limited google-foo: CDP Packet Format: http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/frames.htm#xtocid… CDP Information: http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note091… The latter link says that CDP uses a destination multicast address 01-00-0c-cc-cc-cc, HDLC protocol type 0x2000 on an Ethernet segment. This is where I get lost. Is that an Ethernet MAC broadcast, or a socket-based broadcast? Can I capture those CDP advertisements with asio? Eric

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Binary 1.34 installer
by Luigi Ballabio 12 Jun '07

12 Jun '07

Hi all, I'm one of the developers of a project that requires a few Boost libraries. First of all, thanks to the people at Boost Consulting who made the binary installer available; we have a constant stream of new users asking for instructions on how to build Boost, and let's just say that since the installer was released for version 1.33.1, it streamlined our answers... we still had a few users we couldn't direct to this solution, though; namely, those behind a corporate firewall. Does the new installer for 1.34 work in this setting? I can't test it myself, as I'm not behind such a firewall. Thanks again, Luigi ---------------------------------------- Blessed is the man who, having nothing to say, abstains from giving wordy evidence of the fact. -- George Eliot

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[Pool] pool_allocator with vector-of-vectors ??
by Williams, Alan B 12 Jun '07

12 Jun '07

I have a question about using the standard allocator interface in the boost.pool library. (I'm using boost 1.34.0 with g++ 3.4.3 on redhat linux, in case it matters.) I've successfully used boost::pool_allocator with individual std::vector objects, but I'm having trouble using it with a vector-of-vectors object, like this: std::vector<std::vector<int, boost::pool_allocator<int> > > myvec(1); myvec[0].push_back(99); The "push_back" line causes a seg-fault, which purify says is an array-bounds-write occurring in boost::simple_segregated_storage<unsigned long>::segregate. Am I misusing the pool_allocator? Thanks, Alan

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[mpl] can't transform a map
by Yuval Ronen 12 Jun '07

12 Jun '07

I have the following code: #include <utility> #include <boost/mpl/map.hpp> #include <boost/mpl/transform.hpp> template <typename MplPair> struct make_ptr_pair1 { typedef std::pair<typename MplPair::first *, typename MplPair::second *> type; }; template <typename First, typename Second> struct make_ptr_pair2 { typedef std::pair<First *, Second *> type; }; int main(int argc, char *argv[]) { namespace mpl = boost::mpl; typedef mpl::map< mpl::pair<int, double> > my_map; //typedef mpl::transform< my_map, make_ptr_pair1<mpl::_1> >::type ptr_pair_seq1; //typedef mpl::transform< my_map, make_ptr_pair2<mpl::_1, mpl::_2> >::type ptr_pair_seq2; return 0; } If I uncomment any of the two mpl::transform lines in main(), the code doesn't compile (VC8). The point is to get a sequence of std::pairs out of the content of the mpl::map. Is there anything I'm doing wrong? Can mpl::transform be used for mpl::map? Maybe I can do it with fusion, but the above code seems to be something that's supposed to be working, isn't it? Yuval

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sun studio 8 5.5 and boost
by Christophe Delarue 12 Jun '07

12 Jun '07

HI boost users, I allready post this request : is boost compatible with compiler sun studio 8 C++ 5.5 ? We are trying to compile boost spirit to use the xml serialization, but we got compiler error on : CC -V CC: Sun C++ 5.5 2003/03/12 + /Soft/sunstudio/8/bin/CC +d -g -xs -mt -DBOOST_ALL_DYN_LINK=1 + -DBOOST_ALL_NO_LIB=1 -I. -I/Home/ut0bcm/Boost/boost_1 _34_0 + -I/Soft/sunstudio/8/prod/include/CC/stlport4 -I/usr/include + -library=stlport4 -c -o bin.v2/libs/wave/build/sun/debug/threading-multi/instantiate_cpp_exprgrammar.o libs/wave/src/instantiate_cpp_exprgrammar.cpp "./boost/spirit/phoenix/actor.hpp", line 345: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(phoenix::A&) const. "./boost/ spirit/phoenix/actor.hpp", line 354: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(phoenix::A&, phoenix::B&) const. "./boost/spirit/phoenix/actor.hpp", line 354: Error: Too many args in template, from phoenix::B on ignored. "./boost/spirit /phoenix/actor.hpp", line 363: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(phoenix::A&, phoenix::B&, phoenix::C&) const. "./boost/spirit/phoenix/actor.hpp", line 363: Error: Too many args in template, from phoenix::B on ignored. "./boost/spirit /phoenix/actor.hpp", line 373: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(phoenix::A&, phoenix::B&, phoenix::C&, phoenix::D&) const. "./boost/spirit/phoenix/actor.hpp", line 373: Error: Too many args in template, from phoenix::B on ignored. "./boost/spirit /phoenix/actor.hpp", line 382: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(phoenix::A&, phoenix::B&, phoenix::C&, phoenix::D&, phoenix::E&) const. "./boost/spirit/phoenix/actor.hpp", line 382: Error: Too many args in template, from phoenix::B on ignored. "./boost/spirit /phoenix/actor.hpp", line 397: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(phoenix::A&, phoenix::B&, phoenix::C&, phoenix::D&, phoenix::E&, phoenix::F&) const. "./boost/spirit/phoenix/actor.hpp", line 397: Error: Too many args in template, from phoenix::B on ignored. "./boost/spirit /phoenix/actor.hpp", line 589: Error: Could not find a match for phoenix::actor<phoenix::BaseT>::operator()(const phoenix::unpack_tuple<phoenix::actor<phoenix::BaseT>::TupleT>&) const. -- -- Christophe Delarue mailto:christophe.delarue@gmail.com

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how to Serialize boost::Multiaray
by Alejandro Rubinos Carbajal 12 Jun '07

12 Jun '07

I want to know how can i serialize with boost::serialization a two dimensions boost::multiarray.

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bjam upgrade issue
by Joe Angell 12 Jun '07

12 Jun '07

Hello, After upgrading bjam from version 03.01.11 to 03.1.13 I ran into an issue that is not backwards compatible, and I am wondering if someone has an alternative solution. actions svn_export { svn export $(>) $(<) } make $(TOP)/oak/test/out/SMALL/ : $(TOP)/test/xylem_test_data/SMALL/ : svn_export ; This make rule no longer works in the 3.1.13 version upon directories as targets (works fine for file targets). Any suggestions? Thanks, -- --------------- Joe Angell Boulder Labs, Inc. 7105 LaVista Pl Suite 200 Niwot, CO 80503 (303) 817-8252

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Newbie Boost::Graph - How to write to a .dot file
by Erica Calogero 12 Jun '07

12 Jun '07

Hi there, I am having difficulty writing to a .dot file. After typing in the follwoing code (following the example in the book, p.85). write_graphviz("ECgraphs/test_network.dot",angle_list); I get the following error message: Error 89 error C2664: 'boost::write_graphviz' : cannot convert parameter 1 from 'const char [26]' to 'std::ostream &' What code do I have to write to convert my 'const char [26]' to a 'std::ostream &'? Thanks, Kind regards, Erica.

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MPL intersection of type sequences and compile-time performance
by Andrej van der Zee 12 Jun '07

12 Jun '07

Hi, Sorry if this already has been posted, but I have a problem with compile-time performance when trying to get the intersection of two type sequences. For example, when I do something like this: template<typename list1, typename list2> struct intersect { typedef typename boost::mpl::remove_if<list1, mpl::not_< mpl::contains<list2, mpl::_1> >::type type; }; typedef mpl::vector<a,b,...,z> l1; typedef mpl::vector<c,e,t,u,v> l2; typename intersect<list1,list2>::type my_intersection; Then for large type sequences compile-time becomes unacceptable (O(M*N)). Is there a better way to do this? Thanks, Andrej ___________________________________________________________ To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com

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[boost::filesystem::path] does it work on windows?? please
by jono 12 Jun '07

12 Jun '07

i won't even include my code. anyone?

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How can i kill boost::thread?
by Meryl Silverburgh 12 Jun '07

12 Jun '07

Hi, If I create a thread using boost::thread() library? boost::thread thrd( &DoWork ) ); How can I kill "thrd" later on? Thank you.

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Performing static_cast<shared_ptr<base>*> on a shared_ptr<derived>*. Any guarantees?
by Pete Bartlett 11 Jun '07

11 Jun '07

I have taken over some code that boils down to ///begin code #include <iostream> #include <boost/shared_ptr.hpp> struct base { int i; base(int i_):i(i_) {} }; struct derived : base { derived(int i): base(i) {} }; int main() { boost::shared_ptr<derived> pd(new derived(5)); void* ptr_to_pd = &pd; boost::shared_ptr<base>* ptr_to_pb = static_cast< boost::shared_ptr<base>* >(ptr_to_pd); std::cout << "\n" << (**ptr_to_pb).i ; //Prints 5 } ///End code Now shared_ptr<B> and shared_ptr<A> are unrelated types, so IIUC there is no guarantee that this will work. Is that right? I know from the shared_ptr documentation that I should refactor in the direction of dynamic_ptr_cast (though complications not shown in the code above make that harder that). However for the time being this code appears to be working. Is that just a fluke? I.e. I am relying on the author of boost::shared_ptr and/or my compiler creators not to do something such that it doesn't work. Is there the possibility that any memory could be deleted twice? Or I am worrying over nothing and in fact there is a reason why the above is safe? Many thanks for any advice you can provide, Peter Bartlett

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[bind] Help with functional composition of shared_ptr::use_count in std::map
by Hughes, James 11 Jun '07

11 Jun '07

Hello all, I'm trying to use bind to help with removeif in a std::map<string, shared_ptr<something> >. I want to remove items where the shared_ptr use_count is 1. map<string, shared_ptr<data> > Fred; RemoveIf(Fred.begin(), Fred.end(), boost::bind(std::equal_to<long>(), 1, boost::bind(&map<string, shared_ptr<data> >::value_type::second::use_count, _1) ) However, I get a compile error on ::second not being a class or namespace. Anyone know how I should do this? I'm a beginner at boost::bind, so be gentle.... James This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.

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Re: [Boost-users] [bind] Help with functional compositionofshared_ptr::use_count in std::map
by Küppers, Ben 11 Jun '07

11 Jun '07

> map<string, shared_ptr<data> > Fred; > > RemoveIf(Fred.begin(), > Fred.end(), > boost::bind(&map<string, shared_ptr<data> > >::value_type::second::unique, _1) > ) James, remove_if requires an assignment operator on the operated type but the value_type of a map is defined as std::pair< const T1, T2 >. The const on the first type will cause any assignment to fail. In other words, you can't use remove_if on a map. That said, in order to fix your bind you would need two functors. The type passed to the bind is the value_type of the map which is by definition a pair. You need to first invoke a functor on the pair to extract the second member and then call the member unique on the resulting smart pointer. In order to do so you'll need to write your own extractor, because the STL does not provide a functor to obtain the "second" field from a pair (I haven't found one in boost either). template< class Pair > struct second_of : std::unary_function< Pair, typename Pair:second_type > { typename Pair::second_type opertator()( const Pair& the_pair ) const { return the_pair.second; } }; std::for_each( Fred.begin(), Fred.end(), boost::bind( boost::shared_ptr< data >::unique, boost::bind( second_of< std::map< std::string, boost::shared_ptr< data > >::value_type >(), _1 ) ) ); Note that you can call for_each as it does not require the assignment operator. Hope this helps, Ben This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Thank you.

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Problems with boost.thread
by luca regini 11 Jun '07

11 Jun '07

I have some problems with boost.thread (version 1_34) under gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-52). The library ( all the boost distribution) compiles fine and a bjam on the ./libs/thread/test directory also report a successful test execution. However when i try to explicitly link one of the example (tread_group with the boost tread library using the following command line: g++ -I/opt/six/boost_1_33_1 -I/opt/six/boost_1_34/include/boost-1_34 -pthread -o mytest thread_group.cpp libboost_thread-gcc32-mt-d-1_34.so.1.34.0 i get a segmentation fault. >From a core dump i can see the following stacktrace: 0 0x008e78fb in boost::function0<void, std::allocator<boost::function_base> >::assign_to_own (this=0xb75e5420, f=@0xbfffacb0) at ../../../boost/function/function_template.hpp:647 647 f.vtable->manager(f.functor, this->functor, (gdb) backtrace #0 0x008e78fb in boost::function0<void, std::allocator<boost::function_base> >::assign_to_own (this=0xb75e5420, f=@0xbfffacb0) at ../../../boost/function/function_template.hpp:647 #1 0x008e748f in function0 (this=0xb75e5420, f=@0xbfffacb0) at ../../../boost/function/function_template.hpp:527 #2 0x008e6748 in thread_proxy (param=0xbfffac20) at ../../../libs/thread/src/thread.cpp:106 #3 0x0040f371 in start_thread () from /lib/tls/libpthread.so.0 #4 0x001d8ffe in clone () from /lib/tls/libc.so.6 Where is the problem?? Thanks in advance, Luca Regini

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Question about boost mutex
by Meryl Silverburgh 11 Jun '07

11 Jun '07

Hi, I have a application which uses p_thread for creating threads, can i use the boost mutex classes for thread synchronization? Or the boost mutex class only works with boost thread class? Thank you.

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