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[smart_ptr] Moving cast for unique_ptr
by Karolin Varner 21 Dec '15

21 Dec '15

Hi all! There is the family of boost pointer cast (boost::static_pointer_cast, boost::dynamic_pointer_cast, ...) that allow a developer to write generic code by casting pointers regardless of whether they are some smart pointer (e.g. shared_ptr) or plain pointers. However, those functions have not been implemented for unique_ptr, because they create a copy of their pointer and unique_pointers can not be copied. In my case I still needed to cast some unique_ptr and since it's ok to move unique_ptrs I wrote a function that does exactly that. The code is below – Comments are very, very welcome. It works for my case, but I am sure it is not as generic and safe as it should be ;) . Specifically, for a library, it should be made to work on any kind of smart/plain pointer. Not just unique_ptr. Is there any interest to include a boost::static_moving_pointer_cast and the other types of casts in boost? Best, Karolin /// Dynamic cast a unique_ptr. /// /// This function shall move the pointer in in_ptr, into /// a new unique_pointer of the desire type, dynamic_casting /// it in the process. /// In given pointer shall contain a NULL pointer afterwards. /// /// If unsuccessful, function shall throw an error and leave /// in_ptr unmodified. /// /// This behaviour contrasts a bit with the behaviour of the /// normal dynamic_cast: /// 1. dynamic_cast copies objects, this moves them since /// unique_pointers can not be copied. /// 2. dynamic_cast returns a NULL pointer if the pointer to /// cast is of an incomplete type, this throws /// incomplete_cast instead, to ease error handling. /// /// @tparam T The type to convert to (as non-pointer) /// @tparam F The type to convert from (as non-pointer) /// @param in_ptr The unique_ptr to cast /// @return in_ptr, cast to the desired type template<typename T, typename F> std::unique_ptr<T> dynamic_moving_pointer_cast(std::unique_ptr<F> &in_ptr) { // Exception safety: If The dynamic cast throws an error, // or of we throw incomplete_cast, in_ptr will still be // unmodified T *plain_out_ptr = dynamic_cast<F*>(in_ptr.get()); if (plain_out_ptr == NULL && in_ptr.get() != NULL) throw incomplete_cast(); // Exception safety: Both operations are noexcept in_ptr.release(); return std::unique_ptr<T>(plain_out_ptr); }

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safe::map
by Karen Pease 21 Dec '15

21 Dec '15

Hi everyone - I'm new to boost-devel, and am a bit intimidated ;) I recently finished a project and I don't know if the boost community would have any interest in it, whether it's really "boost material" or not: https://github.com/KarenRei/safe-map The page goes into more detail, but the short of it is: after searching and a long conversation on StackExchange, I discovered that while there are threadsafe ordered-map containers out there, the threadsafety was a bit weak. For example, if you have Thread A iterating across the map and Thread B thread just happens to delete an element as A is passing by, A's iterator becomes invalidated and the program crashes - even in a supposedly "threadsafe" map. For the type of multithreaded cache that I needed, I needed a structure that had the thread safety level of a filesystem - you know, where multiple processes can have file descriptors open at a time and one process might even potentially delete a file that another is accessing, without leading to a system crash. And that's basically what I implemented: safe::map, which not only ensures that basic operations on the container itself are threadsafe, but that everything you do with the iterators - even deleting elements out of the map that other iterators are pointing to - is also threadsafe. It does this by implementing reference counting on the elements in the map and flagging elements for deletion rather than deleting them immediately. A more detailed description of usage, performance, implementation, use cases, etc is on the project page. The project comes with a test suite which launches a number of threads that endlessly randomly tweak and iterate around the map with every function available to them. Does this sound like something that might be useful in boost (after whatever changes would be required)? If there's no interest, no harm done :) - kv, Karen

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[Travis] All boostorg builds stalled?
by Louis Dionne 20 Dec '15

20 Dec '15

Hi, All of Hana's builds are currently stalled [1]. It has been like this for 2 or 3 days. I tried contacting Travis' support, but they are in vacation until January 4th. It also seems like the builds for Predef have been stalled for a while [2]. Perhaps other libraries are also touched. Strangely, builds for non-Boost repositories are not stalled, since I can build personal projects just fine. Does anyone know what might be happening? Louis [1]: https://travis-ci.org/boostorg/hana/builds [2]: https://travis-ci.org/boostorg/predef/builds/97532851

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[gsoc]Seeking Guidance
by Ibrahim Dalal 20 Dec '15

20 Dec '15

Hi I am a sophomore, majoring in Computer Science. I am also a GSoC'16 aspirant. Its the first time I would be contributing to an open source project. Can someone please guide to a small project/patch suitable for a beginner? I have familiarity with C++ programming language along with basic understanding of C and Python. Also have some elementary knowledge of Git. Thanks

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Boost 1.60.0 has been released
by Marshall Clow 18 Dec '15

18 Dec '15

Release 1.60.0 of the Boost C++ Libraries is now available. These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. This release contains one new library and numerous enhancements and bug fixes for existing libraries. New Libraries * VMD: Variadic Macro Data library, from Edward Diener For details, including download links, see http://www.boost.org/users/news/version_1.60.0 You can also download directly from SourceForge: http://sourceforge.net/projects/boost/files/boost/1.60.0/ Tom Kent has made pre-built windows binaries, and they are available at: https://sourceforge.net/projects/boost/files/boost-binaries/1.60.0/ To install this release on your system, see http://www.boost.org/doc/libs/release/more/getting_started/index.html Thanks, --The Boost release team Vladimir Prus Rene Rivera Marshall Clow Eric Niebler Daniel James Beman Dawes

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[variant] Opinion on boost::safe_get<> and default boost::get<> behavior
by Antony Polukhin 18 Dec '15

18 Dec '15

Hi all, I'm in doubt and would like to hear opinions on the following issue. boost::get for boost::variant was not making any compile time checks, resulting in runtime errors where a compile time error must be: boost::variant<int, string> v(100); boost::get<bool>(&v); // returns NULL instead of compile time error boost::get<bool>(v); // throws exception on runtime instead of compile time error Now we have an implementation of compile time checked get in a separate branch at git: boost::variant<int, string> v(100); boost::safe_get<bool>(&v); // compile time error boost::safe_get<bool>(v); // compile time error boost::unsafe_get<bool>(&v); // returns NULL instead of compile time error boost::unsafe_get<bool>(v); // throws exception on runtime instead of compile time error I'm in doubt, what the default behavior of boost::get must be: * safe_get behavior is much closer to Standard Library behavior (just like std::get for tuples) and allows to avoid errors in user code * unsafe_get behavior is same as behavior of old boost::get and won't break user's code if boost::get is used in some generic contexs What's your opinion? -- Best regards, Antony Polukhin

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[QVM] Boost.QVM formal review is ongoing
by Adam Wulkiewicz 18 Dec '15

18 Dec '15

Dear Boost community, It seems that there are some problems with gmane.org related to handling of messages sent to many mailing lists at once. Therefore I'm reposting the information about the formal review. I appologize those of you who recieve this message for the second time. The formal review of Emil Dotchevski's QVM library begined on 7th Dec and it ends on 16th Dec. Boost QVM defines a set of generic functions and operator overloads for working with quaternions, vectors and matrices of static size with the emphasis on 2, 3 and 4-dimensional operations needed in graphics, video games and simulation applications. While it provides its own quaternion, matrix and vector types, it is designed to work primarily with user-defined types through user specializations of the q_traits, v_traits and m_traits templates. QVM's source code is available on Github: https://github.com/zajo/boost-qvm Full documentation is also viewable on Github: http://zajo.github.io/boost-qvm/ We encourage your participation in this review. At a minimum, kindly state: - Whether you believe the library should be accepted into Boost * Conditions for acceptance - Your name - Your knowledge of the problem domain. You are strongly encouraged to also provide additional information: - What is your evaluation of the library's: * Design * Implementation * Documentation * Tests * Usefulness - Did you attempt to use the library? If so: * Which compiler(s) * What was the experience? Any problems? - How much effort did you put into your evaluation of the review? More information about the review process can be found here: http://www.boost.org/community/reviews.html We await your feedback! Best regards, Adam Wulkiewicz

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[qvm] Formal review for QVM
by Adam Wulkiewicz 18 Dec '15

18 Dec '15

Dear Boost community, The formal review of Emil Dotchevski's QVM library begins on 7th Dec and ends on 16th Dec. Boost QVM defines a set of generic functions and operator overloads for working with quaternions, vectors and matrices of static size with the emphasis on 2, 3 and 4-dimensional operations needed in graphics, video games and simulation applications. While it provides its own quaternion, matrix and vector types, it is designed to work primarily with user-defined types through user specializations of the q_traits, v_traits and m_traits templates. QVM's source code is available on Github: https://github.com/zajo/boost-qvm Full documentation is also viewable on Github: http://zajo.github.io/boost-qvm/ We encourage your participation in this review. At a minimum, kindly state: - Whether you believe the library should be accepted into Boost * Conditions for acceptance - Your name - Your knowledge of the problem domain. You are strongly encouraged to also provide additional information: - What is your evaluation of the library's: * Design * Implementation * Documentation * Tests * Usefulness - Did you attempt to use the library? If so: * Which compiler(s) * What was the experience? Any problems? - How much effort did you put into your evaluation of the review? More information about the review process can be found here: http://www.boost.org/community/reviews.html We await your feedback! Best regards, Adam Wulkiewicz

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QVM Review
by Phil Endecott 17 Dec '15

17 Dec '15

Dear All, This is my review of Emil Dotchevski's QVM library. Thank you to Emil for offering this code. I believe that Boost and/or the standard library would benefit from vectors and matrices. Unfortunately I don't think that this proposal is what is needed, and I feel it should not be accepted. I have previously posted my thoughts about the terseness of the identifiers used and the use of operator,; I won't repeat the details here but in summary I find the syntax not to my taste, and not suitable for "public" code. Boost should aim to promote best practice, and I think this library falls short. Now, it's not unusual to find libraries that have interfaces that we don't like. Often we'll use them anyway because the features that the libraries provide outweigh the pain of using them. Does this apply in the case of QVM? Actually since first looking I've found that it does have more functionality than I thought - for example, I've only just found that it has functions to create matrices representing rotations (but not any other affine transformations) and to compute the inverse of a matrix (but not the determinant). But there's still not enough meat here for me to think it's worth using. If this were a comprehensive matrix algebra library, or a computational geometry library, or a SIMD library, then it might be worth putting up with the syntax. But it isn't, it's just a medium-size collection of operators and functions for quaternions, vectors and matrices that many projects will already having amongst their own local utilities. What it does offer is the ability to wrap existing matrix and vector classes and use a single unified syntax for all of them. It's just a shame that the single unified syntax is not the one I want to use! It is interesting to contrast QVM with Boost.Polygon and Boost. Geometry. The similarity is that both of these also wrap existing classes (for e.g. points) by traits class specialisations. When these were reviewed we discussed extensively how support for this compromised the friendliness of the syntax, i.e. the need to write get<0>(p) rather than p.x. What we ended up with there was I think the best that we could do, and it was probably worthwhile because of the substantial core functionality of each of those libraries. In my opinion, QVM doesn't reach that threshold. To address some of the "standard questions": I've not looked at the code, only the docs; I've spent a couple of hours this time and also looked when it was first proposed; and yes I do use vectors and matrices in my own code, for various graphics and cartographic purposes. Regards, Phil.

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Re: [boost] [Boost-users] Boost 1.60.0 rc1 is now available
by Marshall Clow 17 Dec '15

17 Dec '15

Thanks to everyone for testing and reporting back the problems with the RC. I have pinged Vicente about the Boost.Thread problem, and Sebastian about the Boost.PropertyTree warning supression patches. Antony is looking into the Boost.LexicalCast issue. After surveying the other release managers, none of these issues is worth holding up the release for (which would probably stretch to after the new year). We're going to "go with what we have" for the 1.60.0 release, and get these problems fixed for 1.61.0 -- Marshall

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