January 2009 - Boost-users - lists.boost.org

Problem with boost::any?
by Germán Diago 25 Feb '09

25 Feb '09

Hello. I'm working with boost::any and shared_ptr. I'm implementing a plugin system which uses registration from .so files (under Linux). The problem is that I have a factory function which returns boost::any. This boost::any object holds a pointer type. The problem is that when I try to get the registered type back to its real type through boost::any_cast, the cast always fails. If I register this type in the same executable as the application, everything is ok, and I can cast back to its real type.I have no idea why this happens: template <class T> struct ObjectFactory { boost::any operator()() const { typedef typename T::interface_type it; it * t = new T(); return t; } }; #define REGISTER_EXTENSION_NODE(extensionpoint, ns) \ namespace { \ static const bool registeredextensionnode = \ ::Gtk::Util::PluginsManager::instance().register_extension_node(#ns "::" #extensionpoint, \ ::Gtk::Util::detail::ExtensionNodeFactory<ns::extensionpoint>()); \ } These are the implied parts of my application. If I use the macro from a .so, it fails. If I use it from the .exe, everything's ok. The registration part seems to work, I checked the size of the containers and so on, and the elements were inserted. Any help how could I solve this? I've been trying to debug the problem for almost 4 hours with no luck.

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[signals2][review] The review of the signals2 library (formerly thread_safe_signals) begins today, Nov 1st
by Stjepan Rajko 22 Feb '09

22 Feb '09

Hello all, The review for the Signals2 library (formerly known as thread_safe_signals) submitted by Frank Mori Hess begins today (Nov 1st) and is scheduled to end on Nov 10th. I would like to thank Franz Alt, Terry Golubiewski, Doug Gregor, Ravikiran Rajagopal and Andrew Webber for making this review possible by committing to reviewing the library. How to submit a review: -------- As usual, EVERYONE is welcome to participate in the review discussions and to submit a review. I strongly encourage participation from reviewers that would examine the library from a purely user standpoint (commenting on the interface and / or the documentation), as well as reviewers that would be willing to look into the details of the implementation (i.e., you don't have to focus on both). Here are some questions you might want to answer in your review (feel free to skip those that don't apply to your analysis): * What is your evaluation of the design? * What is your evaluation of the implementation? * What is your evaluation of the documentation? * What is your evaluation of the potential usefulness of the library? * Did you try to use the library? With what compiler? Did you have any problems? * How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? * Are you knowledgeable about the problem domain? And finally, every review should answer this question: * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Please submit your review either to the list or privately to me by the end of the review period. If you send me a review privately I will forward it to the list so the review can be discussed. If you would prefer me to forward your review anonymously (with your name removed) please indicate that in your e-mail. If you are a first time reviewer, here is some more information to get you started: * http://www.boost.org/community/reviews.html has more information on the review process * the review officially takes place on both the boost dev and boost-user lists, but typically more of the discussion happens on the boost dev list * if you want to get a feel for past reviews, you can find them in the archives (see http://www.boost.org/community/groups.html) - the past review dates are on the review schedule (http://www.boost.org/community/review_schedule.html) Typically, there is a period of discussion between the reviewers and the author, with official reviews coming in towards the tail end of the review period. About the library: -------- * The library can be downloaded from: http://www.boostpro.com/vault/index.php?&directory=thread_safe_signals (latest version is signals2-2008-10-08.zip) * Documentation is also available online: http://www.comedi.org/projects/signals2/libs/signals2/doc/html/index.html * A synopsis: The Boost.Signals2 library (formerly known as thread_safe_signals) is an implementation of a managed signals and slots system. Signals represent callbacks with multiple targets, and are also called publishers or events in similar systems. Signals are connected to some set of slots, which are callback receivers (also called event targets or subscribers), which are called when the signal is "emitted." Signals and slots are managed, in that signals and slots (or, more properly, objects that occur as part of the slots) can track connections and are capable of automatically disconnecting signal/slot connections when either is destroyed. This enables the user to make signal/slot connections without expending a great effort to manage the lifetimes of those connections with regard to the lifetimes of all objects involved. When signals are connected to multiple slots, there is a question regarding the relationship between the return values of the slots and the return value of the signals. Boost.Signals2 allows the user to specify the manner in which multiple return values are combined. * Relationship to Boost.Signals: This is a thread-safe variant of the original Boost.Signals library. There have been some changes to the interface to support thread-safety, mostly with respect to automatic connection management. The following thread offers some more details on the differences between the two implementations, as well as a plan of a phased replacement of Boost.Signals should Signals2 be accepted: http://tinyurl.com/4sqau3 [nabble] The Signals2 FAQ also covers some differences: http://tinyurl.com/576gl6 Kind regards, Stjepan (review manager)

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Re: [Boost-users] boost geometry lib
by Barend Gehrels 17 Feb '09

17 Feb '09

Hi, Sorry for my late reply, was not on this list earlier. Thanks for your interest. As Bruno said we're currently busy with preview 4. There are substantial changes internally, but from user perspective the changes are not so large. Two things I'll mention: 1) > > http://geometrylibrary.geodan.nl/6__transformation__example_8cpp-exampl > > e.html > > shows the geometry library and uBLAS working together The transformation example will be changed (and much more simpler, from user perspective). The new version has internally transformation capacities and strategies can be used to finetune this (still using uBLAS) 2) if you plan to use the linestrings, note that the algorithms currently take line.begin() and line.end(). This is changed in the new version to just "line", using the boost range library. Preview 4 is expected this month or the beginning of February. Barend Gehrels Geodan, Amsterdam

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[boost-users][asio] timeout - is io_service.reset() safe with pool of threads?
by tomasz jankowski 10 Feb '09

10 Feb '09

hello, I'm implementing timeouts according to suggestion placed here http://lists.boost.org/Archives/boost/2007/04/120339.php because I still don't understand fully how io_service work I have question: is this way of implementation of timeout safe when I'm using pool of threads for one io_service? tom ---------------------------------------------------- Kate Winslet i Leonardo DiCaprio znowu razem na ekranie! DROGA DO SZCZĘŚCIA - w kinach od 30 stycznia. Zobacz zwiastun: http://klik.wp.pl/?adr=http%3A%2F%2Fcorto.www.wp.pl%2Fas%2Fszczescie.html&s…

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[Proto] implementing an computer algebra system with proto
by Kim Kuen Tang 09 Feb '09

09 Feb '09

Hi all, considering the following expression created with proto: "3 *var_+5=2; .. The tree would be : = / \ + 2 / \ * 5 / \ 3 var_ Here the term "var_" is somewhat a placeholder. I wonder wheter it is possible now to change the structure of the tree. That is i want to define a grammar that is able to produce another expression like this. "var_=(2-5)/3;" In tree: = / \ var_ div / \ - 3 / \ 2 5 With this expression i can now define a context that return the final result of the right hand side. But is this possible in proto with the existing functions? This situation is somewhat different from the examples in the documentation. Here i dont want to replace the child node. The whole structure of the input tree should be transformed in another one. Cheers Kim Tang

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[date_time] posix_time::time_duration::operator<< fails for hours>23
by Soren Dreijer 04 Feb '09

04 Feb '09

I'm creating a posix_time::time_duration object based on the minutes() helper function. If I specify a large value, such as 2000, I get a time_duration of 33:20:00. Take a look at the following piece of code, though: time_duration td = minutes(2000); cout << to_simple_string(td); // OK cout << td; // Fails with an assertion in VS2008 The latter call fails with the following assertion in strftime.c on line 658: _VALIDATE_RETURN( ( ( timeptr->tm_hour >=0 ) && ( timeptr->tm_hour <= 23 ) ), EINVAL, FALSE) Apparently, operator<< expands to _expandtime(), which doesn't allow values for the hour to be greater than 23. Is this intended behavior, or should I just always use to_simple_string() rather than the convenient operator<< ?

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Re: [Boost-users] Transferring files across a network.
by Andrew Maclean 03 Feb '09

03 Feb '09

To all those who helped, especially Rahul who very kindly made some sample code available and put me on the right track. I now have a client and a server that can handle multiple files being sent over the network. The files are attached for your interest. If anyone can improve them I really will welcome their comments. If there is a need, it is Ok to include them as examples in the ASIO documentation. I have no issues with this. Thanks once again to everyone who helped. Regards Andrew

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Using SFINAE to detect presence of member function - Unreliable
by Naik, Roshan 03 Feb '09

03 Feb '09

I have taken a look at anything I could find through Boost lists and Google that came up as a solution to the problem of detecting the existence of a member function in a type... using SFINAE. All of them have one problem.. they are unable to detect the existence of the member function if it was defined in a base class. They can only detect if the member function was directly defined in the class being tested. At their heart, all solutions boil down to some variation of the following template class with a template parameter that is a (non-type) pointer to member function: template<class T, void (T::*)(void) > struct Tester; Then we try to SFINAE on it by the usual sizeof trick. However the problem is that if method 'void foo(int)' is defined in a Base class. Then the type of &Derived::foo is actually void (Base::*)(int) ... and not void (Derived::*)(int) Although during argument passing the conversion of the Base member function pointer to Derived member function pointer is acceptable to C++, it will NOT do such conversion when instantiating templates. So trying to use Tester<Derived, &Derived::foo> will always fail us if 'foo' is defined in Base. So .. my question is ....does anyone have solution that works for the case when the method is defined in the base class too ? I am thinking ... if it is possible to extract the class name from the actual type of &Derived::foo, then the problem can be solved... but the type extraction mechanism must not error out on types that have absolutley no member function called foo. I know type erasure (which i prefer to call External polymorhism) can solve this issue but SFINAE is more efficient at runtime. -Roshan

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Re: [Boost-users] Compiler Error With boost::bind and boost::signals
by KERSAM 02 Feb '09

02 Feb '09

I forgot: I am using the Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 14.00.50727.762 for 80x86 and Boost Version 1.35. KERSAM wrote: > > Hello. > > I have a compiler error when I try to use boost::bind and boost::signals. > Here is the code: > > -------------------- > #include<boost/bind.hpp> > #include<boost/signals.hpp> > > class MyBoostTest { > public: > void testFunction(int x, int y) {} > }; > > > void doConnect() { > boost::signal2<void, int, int> signal; > signal.connect(boost::bind<void>(&MyBoostTest::testFunction, new > MyBoostTest, _1)); > } > ----------------------------------- > > The compiler gives me the following error: > c:\3rdparty\boost\boost\bind.hpp(289) : error C2064: term does not > evaluate to a function taking 2 arguments > class does not define an 'operator()' or a user defined conversion > operator to a pointer-to-function or reference-to-function that takes > appropriate number of arguments > > What am I doing wrong? > > Regards > -- View this message in context: http://www.nabble.com/Compiler-Error-With-boost%3A%3Abind-and-boost%3A%3Asi… Sent from the Boost - Users mailing list archive at Nabble.com.

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error linking the boost.filesystem library
by Sean Farrow 01 Feb '09

01 Feb '09

Hi: When trying to build a probram with the boost.filesystem library, I get an lnk1104 using visual studio 8 (2005). The boost include and lib paths c:\program files\boost and c:\program files\boost\bin.v2 are in the default vc include and library paths respectively, the archive bit is set--this shouldn't make a difference as far as I know! Any one know why this error is ocuring? Cheers Sean.

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