- Boost-users - lists.boost.org

multi-type containers
by László Marák 19 Apr '09

19 Apr '09

Dear Boost Users, I am getting started with boost.python. I want to port an image processing library into python. My problem is, that I have several pixel types (like int, float, etc.) which I'd love to handle in the same object by downcasting. In c++ it's something like this: class image {}; class float_image : image { float * pixels; // or boost::array_ptr<float> } class int_image : image { int * pixels; // or boost::array_ptr<int> } I can create the image object by: image * A = new float_image() image * B = new int_image() Now I'd have a virtual functions virtual float image::get_element() virtual int image::get_element() obviously this won't pass in c++, but in python it should pose no difficulty, as python uses dynamic casting. Is there a manner to do this with c++/boost/python? thank you for considering, Laszlo

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installing Windows x64
by John Dlugosz 19 Apr '09

19 Apr '09

The boost-pro installer for Windows didn't download any x64 versions. Is there a different way to get that? TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

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[interprocess]message_queue in Windows service
by Laurence Chambenois 18 Apr '09

18 Apr '09

Hi, I write a Windows Service that answer to requests through a message_queue. The message queue is created by the service, and then by the user starting the service (local system account). When another application, launched by another user, wants to connect to the message queue, it cannot. Because the mapped file is not in the same temporary directory. My question is : how can I do to create a message queue that can be accessed by any user ? Thanks for your help

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Converting an existing thread to use boost.thread
by Sean Farrow 18 Apr '09

18 Apr '09

Hi; I am in the process of converting an existing thread function originally called using BeginThread to use boost.thread. I have a coupple of questions: 1. How would I go about returning to the existing thread, I use windows event handles and when one is signaled the thread ends, can I still use a while loop to do this, such as: Do { Code While(returnFromThread !=true); 2. Does boost::thread allow me the create mutex's and does it inherit windows mutex handles. 3. Can I tell a thread to run as soon as it starts or do I have to use the call boost.join. Any help apreciated. Cheers San. __________ Information from ESET NOD32 Antivirus, version of virus signature database 4018 (20090418) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com

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Exposing std::pair to Python
by A B 18 Apr '09

18 Apr '09

Hi, I am wondering if anyone has a working example of exposing std::pair as a Python tuple or list. Technically, I need to expose a vector of tuples and the following works class_<std::vector<std::pair<std::string, double> > >("VectorPair") .def(vector_indexing_suite<std::vector<std::pair<std::string, double> > >()) ; but I am not sure how then to expose the std::pair. I am guessing I should use boost/python/tuple.hpp or list.hpp but can't figure out the syntax. Thanks in advance.

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[Thread] assertion `!pthread_mutex_lock(&m)' running threaded test
by Rush Manbert 17 Apr '09

17 Apr '09

I have this test program: ------------------------------------------- #include <iostream> #include <vector> #include <boost/thread.hpp> class TestThread { size_t m_loopCount; int m_serverPort; public: TestThread (size_t loopCount) : m_loopCount (loopCount > 0 ? loopCount : 1) , m_serverPort (9090) { return; } void operator() (void) { for (size_t loopCount = 0; loopCount < m_loopCount; ++loopCount) { // Do the same thing the socket open code does char port[6]; sprintf(port, "%d", m_serverPort); char buf0[512]; sprintf (buf0, "%s %zd", "Our loop cont is: " , loopCount); char buf1[793]; sprintf (buf1, "Now the loop count is: %zd", loopCount); // boost::this_thread::yield(); } } }; int main (int argc, char * argv[]) { unsigned int threadLoopCount = 20000; unsigned int threadCount = 2500; // Thread storage std::vector<boost::thread *> threadVec; for (size_t i = 0; i < 1; ++i) { std::cout << i << ": Spawn " << threadCount << " threads with loop count = " << threadLoopCount << std::endl; for (size_t i = 0; i < threadCount; ++i) { TestThread theThread(threadLoopCount); threadVec.push_back (new boost::thread (theThread)); } while (false) <<<-----------------------------------------This block of code disabled { threadVec.at(0)->join(); delete threadVec.at(0); threadVec.erase(threadVec.begin()); TestThread theThread(threadLoopCount); threadVec.push_back (new boost::thread (theThread)); } for (size_t i = 0; i < threadVec.size(); ++i) { threadVec.at(i)->join(); <<<<-----------------------------Error location 1 delete threadVec.at(i); <<<<-----------------------------Error location 2 } threadVec.clear(); std::cout << "Done" << std::endl; } } ------------------------------------------- I haven't edited it to remove disabled code. Note the while(false) which disables the block of code that was starting a new thread as soon as one completed. What the thread code actually does is designed to reveal a different problem. The for loop that only executes once was a failed attempt to make the desired error happen more often. If I run this program enough times in the Xcode debugger, I eventually see the error: ./boost/thread/pthread/mutex.hpp:50: failed assertion `! pthread_mutex_lock(&m)' In the latest case, this happened at the line I have labeled as "Error location 1", but I have also seen this at the line labeled as "Error location 2". I have seen other threads regarding similar errors with boost threads, but nothing says that this was a bug that has been fixed, or that there is something I should do to avoid the error. I'm also wondering if I have misunderstood something about how to use the threads code. I am running Boost 1.36.0 on OSX 10.5.6 with Xcode 3.1.2. Does this look like pilot error, or is it a bug? - Rush

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[program_options] Multitoken and positional options; assertion failure
by Gevorg Voskanyan 17 Apr '09

17 Apr '09

I was playing with program_options in svn trunk after recent fixes for multitoken options and hit an assertion failure with the attached example. The example takes two options - one multitoken and one positional, and simply outputs provided values. The two invocations below work OK: $ bin/gcc-4.2.2/debug/multitoken_positional some_file -m token1 token2 File: some_file Multitoken: token1 token2 $ bin/gcc-4.2.2/debug/multitoken_positional -m token1 token2 --file some_file File: some_file Multitoken: token1 token2 While experimenting with this one asserts: $ bin/gcc-4.2.2/debug/multitoken_positional -m token1 token2 -- some_file multitoken_positional: ../../../../../svn_boost/trunk/libs/program_options/src/cmdline.cpp:295: std::vector<boost::program_options::basic_option<char>, std::allocator<boost::program_options::basic_option<char> > > boost::program_options::detail::cmdline::run(): Assertion `opt2.original_tokens.size() == 1' failed. Aborted Should an exception be thrown instead, or this is a use-case worth to support? Thanks, Gevorg

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[boost-users][bind, lambda, ...] binding unused actual parameter
by Igor R 16 Apr '09

16 Apr '09

Hello, Is it possible somehow to make a binder that stores "unexpected" argument? Motivation: I have to create & pass a callback handler from within intusively ref-counted object (MS-ATL) to an outer asynchronous subsystem. If the object were shared-ptr enabled, I'd do this as usually: ThisObj::handler() { //... } ThisObj::doSomething() { asyncSubsystem_->doSomething(&ThisObj::handler, shared_from_this()); } However, in my case I have to do something like this: asyncSubsystem_->doSomething(&ThisObj::handler, this, mySmartPtr); // store someOtherSmartPtr in the functor, just to ensure "this" won't die before the handler is invoked Is it possible with bind, lambda or some other library? Thanks.

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[filesystem] doc bug
by Michael Fawcett 16 Apr '09

16 Apr '09

A co-worker of mine who usually programs in C# ran across this bug in the filesystem Two Minute Tutorial located here: http://www.boost.org/doc/libs/1_38_0/libs/filesystem/doc/index.htm#tutorial #include "boost/filesystem.hpp" // includes all needed Boost.Filesystem declarations #include <iostream> // for std::cout using boost::filesystem; // for ease of tutorial presentation; // a namespace alias is preferred practice in real code Should be: #include "boost/filesystem.hpp" // includes all needed Boost.Filesystem declarations #include <iostream> // for std::cout using namespace boost::filesystem; // for ease of tutorial presentation; // a namespace alias is preferred practice in real code Note the using statement. --Michael Fawcett

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Re: [Boost-users] Multiple Multitokens
by David Doria 16 Apr '09

16 Apr '09

Volodya, So was my example code way off? Ie. is the short answer that program_options can't take --list a.txt b.txt --list c.txt d.txt and give me 2 vector<string>'s, one containing a.txt b.txt and the other containing c.txt d.txt? Thanks, David

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