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

Boost cookbook site (alpha)
by Kirit Sælensminde 03 Oct '07

03 Oct '07

I've spent the weekend putting together a cookbook site. I hope nobody minds. People can explore and play with it at http://www.boostcookbook.com/ Any problems, issues or suggestions can be reported at http://www.boostcookbook.com/Site:/Issues Apart from a couple of ASP pages using JavaScript the site is in C++ and makes heavy use of Boost :) Kirit

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Reproducible access violation on win64 with signals (example code)
by Nicholas Bastin 02 Oct '07

02 Oct '07

I've managed to get my signals access violation to happen in a relatively simple test program on win64. I'm attaching my example source code to this email. If anyone needs anything else to reproduce the problem, please let me know. This program works when statically linked, but not when dynamically linked, so if someone can spot a bad compiler/linker flag, that would help too. I built boost with: bjam --toolset=intel address-model=64 link=shared runtime-link=shared --with-signals stage Also, I had to edit intel-win.jam to change icc.exe to icl.exe so that the compiler would run properly. I built my test application with: icl /EHsc /MD /I. test.cpp /link /subsystem:console /LIBPATH:stage\lib /NODEFAULTLIB /ENTRY:mainCRTStartup /FORCE:multiple boost_signals-iw-mt-1_34.lib msvcprt.lib msvcrt.lib libirc.lib libmmd.lib If you build with static linkage (obviously, rebuild boost without the shared link settings), the executable works fine (with libboost_signals-iw-mt-1_34.lib). -- Nick

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statechart - time event...implementation ?
by Raja Cherukuri 02 Oct '07

02 Oct '07

It seems the current implementation of statechart library does not have timed event. It is possible to extend or specialize the current event<> class to achieve this ? Has anyone done this yet ? Looks like a common requirement for this type of event. Any reason why it is not part of this library offering ? Is it expected that users of this library do it themselves ? Thanks in advance. - Raja

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Using boost (maybe mpl?) to generalize a switch statement to call different template functions
by Peng Yu 02 Oct '07

02 Oct '07

Hi, I have the following program, which uses a switch statement to call different template functions. The example is simple, but as the number of shapes increase, the switch statement might be very hard to maintain. I'm looking for a more general solution (maybe using mpl, not sure), such that the switch statement can be automatically generated, therefore, more maintainable. Thanks, Peng #include <iostream> enum shape { circle, square // there might be many cases }; template <shape, shape> struct A { void doit() const; }; //doit functions are defined for a majority number of shape combinations (maybe not all, but could be defined for all---the bodies of the functions not need can be empty). // 3 case. There should be 4 doit's if we consider all combinations. template <> void A<circle, circle>::doit() const { std::cout << "circle circle" << std::endl; } template <> void A<circle, square>::doit() const { std::cout << "circle square" << std::endl; } template <> void A<square, circle>::doit() const { std::cout << "square circle" << std::endl; } void f(shape s1, shape s2) { // each defined shape-combination corresponds to one case // I want to generalize the code by using boost::mpl // (or some other packages if applicable) switch(s1 << 8 | s2) { case circle << 8 | circle: A<circle, circle>().doit(); break; case circle << 8 | square: A<circle, square>().doit(); break; case square << 8 | circle: A<square, circle>().doit(); break; default: std::cout << "not defined" << std::endl; } } int main() { f(circle, circle); f(circle, square); f(square, circle); f(square, square); }

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[signals] call a slot only once
by Christian Holmquist 02 Oct '07

02 Oct '07

Hello, Is there a way to automatically have a slot disconnected after it has been called once, without managing the connection manually? void f() { } signal<void()> sig; sig.connect(&f); sig(); // f gets called sig(); // f shouldn't get called

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Usage of iterator_facade and iterator_adaptor
by Peng Yu 02 Oct '07

02 Oct '07

Hi, I'm trying to use Boost.Iterator library. I understand that iterator_adaptor specialize some part of iterator_facade. However, I can not tell for what application I should use iterator_facade or iterator_adaptor. I think the manual should summarize this for the user. Can somebody give me some hint on which to use them and under what condition, if you have the experience? Thanks, Peng

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[boost::enable_shared_from_this] in inheritance tree throws bad_weak_ptr exception
by dariomt＠gmail.com 02 Oct '07

02 Oct '07

I need to create a class hierarchy where every level inherits from boost::enable_shared_from_this. I am having problems caused, I believe, by having more than one copy of enable_shared_from_this. I am using boost 1.34.1 with VS2003 and VS2005, with and without ICL9.1, always getting the same result: a boost::bad_weak_ptr exception. #include <boost/shared_ptr.hpp> #include <boost/enable_shared_from_this.hpp> using namespace boost; struct A : enable_shared_from_this<A> { shared_ptr<A> getA() {return enable_shared_from_this<A>::shared_from_this();} }; struct B : A, enable_shared_from_this<B> { shared_ptr<B> getB() {return enable_shared_from_this<B>::shared_from_this();} }; int main() { shared_ptr<A> pA (new A); pA->getA(); // this works OK shared_ptr<B> pB (new B); pB->getB(); // throws boost::bad_weak_ptr() !? return 0; } question 1: Is this expected or am I doing something wrong? question 2: If it is expected: is it possible to have it explained in the documentation? question 3: Is there a way to accomplish this (inheritance with shared_from_this in all levels) using enable_shared_from_this? Thanks in advance

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[Process] getcwd memory leak in context.hpp
by Chris Fairles 02 Oct '07

02 Oct '07

Valgrinding the single_process_tutorial example, it seems getcwd in context.hpp is called with a NULL buffer and 0 size meaning that space is automagically malloc'd (according to POSIX.1-2001). ==10383== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 5 from 1) ==10383== malloc/free: in use at exit: 64 bytes in 1 blocks. ==10383== malloc/free: 32 allocs, 31 frees, 22,225 bytes allocated. ==10383== For counts of detected errors, rerun with: -v ==10383== searching for pointers to 1 not-freed blocks. ==10383== checked 162,760 bytes. ==10383== ==10383== 64 bytes in 1 blocks are definitely lost in loss record 1 of 1 ==10383== at 0x4A0590B: realloc (vg_replace_malloc.c:306) ==10383== by 0x39848C03FC: getcwd (in /lib64/libc-2.5.so) ==10383== by 0x407894: boost::process::basic_work_directory_context<std::string>::basic_work_directory_context() (context.hpp:85) ==10383== by 0x407A19: boost::process::basic_context<std::string>::basic_context() (context.hpp:142) ==10383== by 0x403730: main (single_process_tutorial.cpp:44) ==10383== ==10383== LEAK SUMMARY: ==10383== definitely lost: 64 bytes in 1 blocks. I think the memory should be free()'d if the returned buf isnt NULL (or create a buffer isntead of passing NULL,0). Chris

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identical boost expression used in different parts of the code - looking for an alias
by e r 02 Oct '07

02 Oct '07

hi for example, i use boost::bind( &A::f, _1 ) in different parts of my code. how can i define an alias for this expression? i'm thinking of using something like some_type* fo = new boost::bind(&A::f,_1); and use *fo in place of boost::bind(...). is this crazy? what should some_type be?

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boost::shared_ptr and "this"-pointer: how to use shared_from_this?
by Taneli R. 02 Oct '07

02 Oct '07

I'm converting pipes and filters architecture made with raw pointers to use shared_ptrs. My Pipe class has a static counter, which gives unique pipeID to every pipe. Since Pipe class has pure virtual functions, the pipes in my architecture are instances of derived classes. Pipe class looks like this: class Pipe { public: Pipe() : pipeID(++pipeCount) {} virtual bool lay(boost::shared_ptr<Pipeable>& source, string& sourceTag, boost::shared_ptr<Pipeable>& destination, string& destTag) = 0; /*...other pure virtual functions here...*/ protected: int pipeID; static int pipeCount; } My problem is that when I try to make a new pipe between source and destination, the pipe is made twice (with different pipeID-numbers), which is a problem because there should be only one pipe connecting my components. I believe it is a result from using "this"-pointer directly without enabling "shared_from_this". I know that I should use it somehow but the same time I should maintain the unique pipeID. If I create a new shared_ptr with "shared_from_this" enabled inside SimplePipe, it has a different pipeID than the one I should be using. I have to use shared_ptr because I'm storing pointers into containers. And finally I cannot instantiate Pipe directly from its base class with using "shared_from_this" because it has pure virtual functions. Any help for solving this problem or a decent tutorial on using shared_ptrs and enable_shared_from_this would be appreciated. The following code snippets illustrate the problem: // //Main // boost::shared_ptr<Pipe> pipe; pipe = inputPipes[tag]; //find a matching pipe from the map if (pipe.get() == 0) //if not found, create a new pipe { boost::shared_ptr<Pipeable> source; // no source boost::shared_ptr<Pipeable> destination (boost::dynamic_pointer_cast<Pipeable>(comp)); pipe = boost::shared_ptr<Pipe>(new SimplePipe(source, srcTag, destination, destTag)); //creating new pipe inputPipes[tag] = pipe; //put the pipe into a map } // //SimplePipe, derived from Pipe // SimplePipe::SimplePipe(boost::shared_ptr<Pipeable>& source, string& sourceTag, boost::shared_ptr<Pipeable>& destination, string& destTag) { lay(source, sourceTag, destination, destTag); } bool SimplePipe::lay(boost::shared_ptr<Pipeable>& source, string& sourceTag, boost::shared_ptr<Pipeable>& destination, string& destTag) { if (source.get() != 0 && destination.get() != 0 && !sourceTag.empty() && !destTag.empty()) //Both ends attached { if (source->makeSource(pipeID, sourceTag)) { this->source = source; //problem? if (destination->makeDestination(pipeID, destTag)) { this->destination = destination; //problem? return true; } else { source->detachPipe(pipeID); } } } else if (source.get() == 0 && destination.get() != 0 && !destTag.empty()) //only destination attached { if (destination->makeDestination(pipeID, destTag)) { this->destination = destination; //problem? return true; } } else if (source.get() != 0 && destination.get() == 0 && !sourceTag.empty()) { /*etc etc...*/ } return false; } -- View this message in context: http://www.nabble.com/boost%3A%3Ashared_ptr-and-%22this%22-pointer%3A-how-t… Sent from the Boost - Users mailing list archive at Nabble.com.

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[boost::graph] creating an external map for depth_first_search
by v r 02 Oct '07

02 Oct '07

I cannot figure out how to create a color map for depth first search, i`m using bundled properties and the following type as graph. adjacency_list<listS,setS,bidirectionalS,WorldNode> world_graph_t; right now i`m trying to make it like this, but i get 50 errors and cannot deduce what my error is. template<class VisitorT> THOR_INLINE void DepthFirstSearch(const VisitorT& vis, const vertex_descriptor& start) { using namespace boost; std::vector<default_color_type> color_vec( num_vertices(graph) ); depth_first_search(graph, visitor(vis), color_map(make_iterator_property_map(color_vec.begin(),get(vertex_color,graph))), start); } --------------------------------- Вы уже с Yahoo!? Испытайте обновленную и улучшенную. Yahoo! Почту!

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Bjam linking problem
by desai3＠cooper.edu 02 Oct '07

02 Oct '07

Hi folks: I have successfully wrapped up a C++ program in Python. Now I want to give my libboost_python.so and server.so files to my friend, so that he can use it too. However server.so makes use of libstdc++ and ssl library files, which I have to link statically to the server.so in order to be able to give server.so to someone. However Bjam is not linking libstdc++.a or libssl.a to server.so statically. I will really appreciate if someone could give me any direction about how to link these libraries statically to server.so . Thank you very much. Maulik P.S. My Jamfile looks like this ----------------------------------------------------------------------- project-root ; import python ; extension server : server.cpp <template>@boost/libs/python/build/extension : <include>. <include>../dqp <include>/export/apps/dq/dqweb/include <library-path>/home/o066144/work_in_progress/api/SunOS-5.8-g++ <library-path>/export/apps/dq/dqweb/lib <library-path>/usr/local/lib <find-library>ssl <find-library>crypto <find-library>dl <find-library>socket <find-library>nsl <find-library>gcc <find-library>stdc++ ; ---------------------------------------------------------------------------

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BGL: traveling salesman problem
by Michael Held 02 Oct '07

02 Oct '07

hi bgl-guys, is there a 'traveling salesman' implementation for bgl or is anything in this direction planned? there are several algorithms available, e.g. http://www.tsp.gatech.edu/concorde.html which could be ported to bgl?! best regards, michael

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dumb question about boost::any.
by chun ping wang 02 Oct '07

02 Oct '07

How would i go about implementing operator< for boost::any....

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[program_options] Why is allow_unregistered not implemented for config file?
by Marty Fried 01 Oct '07

01 Oct '07

I want to use the program_options library for my app's, well, program options. There is one set of options, which will usually only be one or two lines, that will have an unknown name; this is only handled by the (boost::program_options::) basic_command_line_parser template, with, apparently, no equivalent functionality for config files. This seems to me to be an oversight. I would have thought there would at least be an option to ignore unknown parameters if they aren't supported like for the command line. For my needs, it looks like I might need to modify the Boost sources to disable the exception on unknown parameters, or force the user to create a special config file for, most likely, a single parameter. Or I can change the syntax to something much less natural. What I'm hoping for is either someone to inform me that I'm wrong, and there is a way to handle config files more elegantly than what I'm seeing, or a suggestion as to how best to implement what I need. Thanks for any help you can offer. -- Marty Fried - email: public.forums (at) gmail.com Left coast, USA

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Boost license / OSI approved
by Ruediger Berlich 01 Oct '07

01 Oct '07

Hi there, I noticed that the Boost license is not listed as an OSI approved license (see here: http://www.opensource.org/licenses/alphabetical ). Why is this ? The license seems to nicely comply with the Open Source definition, from what I can see (see http://www.opensource.org/docs/osd) http://www.fsf.org/licensing/licenses/ lists it as GPL-compatible. Best Regards, Ruediger

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thread, use case: one manager and several worker threads
by Torsten Mohr 01 Oct '07

01 Oct '07

Hi, i have a question regarding boost::thread on general usage. I have a calculation intense problem that can be parallelised quite well. But i'd like the whole thing to be interruptible, so when the user commands to stop calculationg then the threads should stop working on the problem. I don't know how to set this up in principle, some thoughts: I want to create one manager thread and several worker threads. The manager thread commands the worker threads on what job to work. When a worker thread has finished, it tells the manager thread so and can get another job to work on. If a user commands the manager thread to stop working, the manager thread commands the worker threads to stop as soon as possible. I think these are quite some normal requirements, but i don't know how to implement this using boost::thread. What is the preferred way to send commands to threads? Just lock a mutex that is shared with the thread and then write a shared variable? How can a manager thread wait on several worker threads at once without wasting CPU time? How does a worker thread notify the manager thread? I can't see how this can be done with boost::condition, do i miss something? Or is it possible for the worker thread to share a boost::mutex with every worker thread, let the manager thread lock those mutexes? It then can only do "condition->wait" on _one_ of the conditions. Best regards, Torsten.

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one reason I suspect a build problem in prior post,
by Mike Marchywka 01 Oct '07

01 Oct '07

when I added the code to trap the regex_error, the previously clean build returned the following during linking but I didn't think it would be a problem: Info: resolving vtable for boost::regex_errorby linking to __imp___ZTVN5boost11r egex_errorE (auto-import) I'm linking to /libboost_regex-gcc-mt-1_33_1.a and cygboost_regex-gcc-mt-1_33_1.dll Thanks again. [ I decided to add boost while using my mom's machine and I found out I had accidentally included boost in "her" cygwin install so it is quite likely I botched something ] Mike Marchywka 586 Saint James Walk Marietta GA 30067-7165 404-788-1216 (C)<- leave message 989-348-4796 (P)<- emergency only marchywka(a)hotmail.com Note: Hotmail is blocking my mom's entire ISP claiming it is to reduce spam but probably to force users to use hotmail. Please DON'T assume I am ignoring you and try me on marchywka(a)yahoo.com if no reply here. Thanks. _________________________________________________________________ Test your celebrity IQ. Play Red Carpet Reveal and earn great prizes! http://club.live.com/red_carpet_reveal.aspx?icid=redcarpet_hotmailtextlink2

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date_time time_duration getting milliseconds
by Sebastian Hauer 01 Oct '07

01 Oct '07

Hi Boost Users, I've started using boost's date_time library recently which I find quite convenient for the most part. I have to handle times with sub second parts frequently and was wondering what the recommended way is to extract the milliseconds part of a time_duration instance? It seems there is no time_duration.milliseconds() method available and fractional_seconds() is platform dependent. BTW: I am currently using boost 1.34.1. Regards, Sebastian

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u32regex_search crashes
by Anjaly 01 Oct '07

01 Oct '07

Hello, I am new to Boost-regex library. The libray is build with icu support.The user interface is created using wxWidgets library. I want to search a file using u32regex_search. But the program crashes and the error it shows is 'Invalid UTF-8 sequence encountered while trying to encode UTF-32 character'.I am reading the contents of the file and it is stored in char array.The program is crashing when it encounters a char with hex value 00. wxString s=SearchTxt->GetValue(); const char *start=(const char*)buffer; const char *end=(const char*)buffer+len; boost::cmatch what; boost::u32regex e1= boost::make_u32regex(s.fn_str(), boost::regex::icase); while(boost::u32regex_search(start,end, what,e, boost::match_default)) { cout << what[0] << "\n"; } ______________________________________ Scanned and protected by Email scanner

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Problem in calculating cycle sequence...
by abhishek.v＠tcs.com 01 Oct '07

01 Oct '07

Hi I m able to calculate whether the cycle exist in the graph or not. With the help of following code.. //Finding out cycles struct cycle_detector : public dfs_visitor<> { cycle_detector( bool& has_cycle, int& num):_has_cycle(has_cycle),cycle(num) { } template <class Edge, class Graph> void back_edge(Edge, Graph&) { cycle++; _has_cycle = true; } protected: bool& _has_cycle; int& cycle; }; int main () { ...... .... .... //Finding out whether the graph has cycles.. bool has_cycle = false; int count_cycle=0; typedef Traits::vertices_size_type size_type; cycle_detector vis(has_cycle,count_cycle); boost::depth_first_search(g, visitor(vis)); if(has_cycle) { file_op << "\nThe graph is cyclic"<< std::endl; file_op<<"\nNumber of cycles in the graph is "<<count_cycle; } else std::cout << "The graph is acyclic"<< std::endl; return 0; } Now what i want is to calculate the vertex between which the cycle exist ... How to calculate that.. Thanks Abhishek Vyas Tata Consultancy Services Mailto: abhishek.v(a)tcs.com Website: http://www.tcs.com ____________________________________________ Experience certainty. IT Services Business Solutions Outsourcing ____________________________________________ =====-----=====-----===== Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you

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string_algo no replace_if
by gast128 01 Oct '07

01 Oct '07

Dear all I was requesting an 'erase_if' a while ago, and now I ran into a 'replace_if' problem. So after spendig 2 hours in the documentation, I finally found on www ('[string_algo] replace repeated char with single instance?') that one should use the 'find_format_all': boost::find_format_all(str, boost::token_finder(boost::is_any_of("ab")), boost::const_formatter("c")); But wouldn't it be better to make a 'replace_if' shortcut solely for the purpose of documentation reasons: boost::replace_all_if(str, boost::is_any_of("ab"), "c"); I think that most people find the last line easier to read and comprehend than its (more powerful) 'find_format' cousin. The string_algo library is nice but I get lost more than once. Especially find, replace, erease with predicates are often used by us. However direct use seems not possible. wkr, me

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Passing extra compiler arguments with bjam
by Cory Nelson 01 Oct '07

01 Oct '07

I'm wanting to pass some extra arguments for VC++ whole program optimization (specifically, /GL to the compile, /LTCG to the linker). Does anyone know how? -- Cory Nelson

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Problem in calculating critical path and fundamental ckts
by abhishek.v＠tcs.com 01 Oct '07

01 Oct '07

Hi.. I want to calculate the critical paths of a graph using BGL. So what i did is i calculated the connected components of a graph then remove the edge one by one if the number of connected component increase then the edge is critical edge or a bridge. This works fine in case of undirected graph. But how do i calculate connected component of a directed or Bidirected graph i m able to calculate the strongly connected component but it is not helping me out. Can you suggest me something regarding this. Also i want to calculate the fundamental ckt that exist in a graph now. What i did here is i m calculating K-MST. Now i want to calculate the fundamental ckt how should i do that... Thanks Abhishek Vyas Tata Consultancy Services Mailto: abhishek.v(a)tcs.com Website: http://www.tcs.com ____________________________________________ Experience certainty. IT Services Business Solutions Outsourcing ____________________________________________ =====-----=====-----===== Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you

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Inquiring about the feasibility of boost::mpl based statechart DSELs that generate boost::statechart based components
by Tony Turner 01 Oct '07

01 Oct '07

Greetings; I am currently experimenting with the feasibility of writing a boost::mpl based library of metaprograms that process statechart DSEL language phrases ( see ref #1 below), that then specifically generate boost::statechart based components. I would be most grateful to hear from others regarding both difficulties to this approach, as well as success stories. If this approach seems feasible, I would like to contribute the resultant code back to the open source community. Since I'm not sure how the contribution process works, I would appreciate it if someone could point me in the right direction. Reference (#1) ( the statechart developed in chap 11, "A DSEL Design Walkthrough" in Abrahams and Gurtovoy's "C++ Template Metaprogramming book".) Thankyou very much for your time; Tony Turner R&D Software Engineer

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