February 2013 - Boost-users - lists.preview.boost.org

[LockFree] a queue of std::shared_ptr?
by Scott Smedley 22 Feb '13

22 Feb '13

Hi all, Is it possible to store std::shared_ptr objects in a boost::lockfree::queue? eg. boost::lockfree::queue<std::shared_ptr<Message>> q; gcc 4.7.2 with Boost 1.53.0 is giving a static assertion failure. It wants: boost::has_trivial_destructor<T>::value and boost::has_trivial_assign<T>::value Any help would be muchly appreciated. Scott.

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scope_lock question
by Jeff Dunlap 22 Feb '13

22 Feb '13

I plan to start using Boost Thread, but for now I have a multithreaded Win32 application that does not use boost. Although the threads were not created with Boost Thread, can I use boost::mutex::scoped_lock to protect some new functions I write for the app? Example: boost::mutex mutex; void whatever() { boost::mutex::scoped_lock lock(mutex); // will this be protected even though the // thread was not created using Boost? } Thank you

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[Building] Weird crash on windows while trying to build boost
by Alessandro Stamatto 21 Feb '13

21 Feb '13

Hi, I'm trying to build Boost on windows 7, I'm using rubenv mingw+gcc-4.8 (from here: http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20W… ). I tried the usual way: "bootstrap gcc" and ".\b2". But at the beginning of the building process a weird crash happens with a windows message dialog of "Keyboard History Utility has stopped working". It happens even with the suppressing option ('-d0'). In the process list I see that this Keyboard Utility is called "doskey.exe". What is happening? Is it possible to build boost with gcc-4.8 on windows? Thanks for your attention, Alessandro Stamatto.

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New gil::io has been added
by Christian Henning 21 Feb '13

21 Feb '13

Hi all, I have successfully replaced the old gil::io extension with the new gil::io. The new io has been developed on and off over the last few years and I believe it's a great improvement over the old one. Before going into details I like thank everyone that has been helping me out along the way. I have learned a lot of things and I'm very grateful for the experience! There are numerous improvements and perhaps it's best to study the documentation before using it. Here are some noteworthy points that come to my mind: * updating code that uses the old version only requires to change the header from "boost/extension/io/jpeg_io.hpp" to "boost/extension/io/jpeg/jpeg_io_old.hpp" * new formats: bmp, pnm, raw, targa * read numerous meta information from images. See boost/gil/extension/io/png_tags.hpp for example. * use all sorts of file metaphers or file names, like FILE*, ifstream, stringstream, wstring, filesystem::path, etc * in-memory images are supported * read large images with a scanline_read_iterator * have access to the file format backend * etc. There are some items left for which I need help from the boost maintainers. * How do I hook up the gil::io documentation so it's build when all boost documentation is build? * Same for the test suite. * Should I update boost_release? Or should the new extension "simmer" for a while? Again thanks for everything, Christian

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time out for r_c_shortest_paths
by Brammert Ottens 21 Feb '13

21 Feb '13

Hi, I want to be able to put a time out on the r_c_shortest_paths, and still be able to get the optimal paths that have been found so far. Currently, I changed the REF such that it always returns false as soon as the time out has reach, in effect emptying the unprocessed_labels queue. The problem with this is that the algorithm still needs quite some time to actually empty the queue. I tried to have the on_label_popped(cur_label) throw an exception when the timeout has been reached. The timeout itself works like a charm, but because the pareto_optimal_solutions container is only filled after the while loop I can't access the already found optimal solutions. Does anybody have an idea on how to do this in a better way, without having to request an addition to the boost API? Regards, Brammert

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upgrading lock
by Igor R 21 Feb '13

21 Feb '13

Hello, Just wanted to be sure that I'm doing this correctly. typedef boost::upgrade_lock<boost::shared_mutex> upgrade_lock; typedef boost::upgrade_to_unique_lock<boost::shared_mutex> upgrade_to_unique_lock; upgrade_lock readLock(mutex_); // accessing shared resources in read-only mode //... upgrade_to_unique_lock writeLock(readLock); // modifying shared resources Is the above correct? In particular, upgrade_lock acquires "read" lock in raii style (similarly to shared_lock), right? Thanks.

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Re: [Boost-users] Can boost help me organize/parse lots of binary data?
by Gabriel Bizzotto 21 Feb '13

21 Feb '13

Chris, > class Item > { > virtual void Decode(istream& Stream) = 0; > } > class Double : public Item > class String : public Item > class EmployeePacket > { > std::vector<Item*> Items; ... Maybe boost::any will do better here ? http://www.boost.org/doc/libs/1_53_0/doc/html/any.html

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[lockfree] compile-time capacity vs. run-time capacity
by Akira Takahashi 21 Feb '13

21 Feb '13

Hi, I confused with boost::lockfree::queue behavior. Fist, run-time capacity: #include <iostream> #include <boost/lockfree/queue.hpp> int main() { boost::lockfree::queue<int, boost::lockfree::fixed_sized<true>> que(3); std::cout << std::boolalpha; std::cout << que.push(1) << std::endl; // true std::cout << que.push(2) << std::endl; // true std::cout << que.push(3) << std::endl; // true std::cout << que.push(4) << std::endl; // false } I think this behavior is correct. But, compile-time capacity: #include <iostream> #include <boost/lockfree/queue.hpp> int main() { boost::lockfree::queue<int, boost::lockfree::capacity<3>> que; std::cout << std::boolalpha; std::cout << que.push(1) << std::endl; // true std::cout << que.push(2) << std::endl; // true std::cout << que.push(3) << std::endl; // false : why? std::cout << que.push(4) << std::endl; // false } Is this bug or specification? Thanks, Akira >>======================== Akira Takahashi mailto:faithandbrave@gmail.com site: https://sites.google.com/site/faithandbrave/about/en

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Coroutine documentation question
by Brian Wood 21 Feb '13

21 Feb '13

I have a question about a sentence on this page: http://www.boost.org/doc/libs/1_53_0/libs/coroutine/doc/html/coroutine/intr… "The principal difference between coroutines and routines is that a coroutine enables explicit suspend and resume their progress via additional operations by preserving local state ..." I'm wondering if it would be accurate/helpful to change that to this: "The principal difference between coroutines and routines is that coroutines enable explicit suspend and resume of their progress via additional operations by preserving local state ..." Shalom Brian Wood Ebenezer Enterprises - so far G-d has helped us. http://webEbenezer.net (651) 251-9384

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Boost.Geometry: Correct use of multi-part polygons
by John Lilley 20 Feb '13

20 Feb '13

Greetings, I am looking for some guidance around the correct creation and use of multi-part polygons. I am a bit confused about when to use each of the following: * Polygon with multiple rings * Vector of polygons * Polygon set * Set/vector of polygons, each potentially containing multiple rings I gather from this example picture: http://geometrylibrary.geodan.nl/03__polygon__example_8cpp-example.html That if one wants holes to be opened as a result of intersection, they need to be rings as opposed to polygon sets or vectors of polygons? An example would be polygon(s) representing an island chain. Some of the islands are atolls and as such have a hole in the middle. What would a representation of this set of islands look like? And, what If I don't know if I have "real" rings (interior) vs just a collection of polygons (like I got this from an external source that doesn't have the same model). If I just throw a pile of points at a polygon and call clean(), will that magic everything up for me? john

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