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[test] [build] best practices for looking up data files from test executables
by Stefan Seefeld 14 Nov '17

14 Nov '17

Hi there, I'm trying to write a test that needs to access a data file. As I'm surely not the first wanting to use external data in my tests, I wonder whether there are established "best practices" or idioms when using Boost.Build and Boost.Test. My first attempt was to compute the relative path using the test source's `__FILE__`, until I realized the path was invalid due to the build logic moving executables before running them. Then I considered using a command-line option to point at the data directory, but that seems quite involved when using boost::test (and BOOST_TEST_MODULE)... Any suggestions for how to approach this ? Thanks, Stefan -- ...ich hab' noch einen Koffer in Berlin...

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Exceptions vs Assertion for library API?
by Jonathan Biggar 13 Nov '17

13 Nov '17

Any advice in choosing between throwing an exception vs asserting for invalid uses of a library API? I'm building a small "transactional" library I'd like to contribute to boost where certain API calls are constrained to only be valid if the transaction is still "in-progress". Such calls will never succeed, and are easy for the implementation to diagnose. I'd like to have the library fail an assertion, which is far clearer to the user that the code logic is incorrect, but it bothers me that assertions are much more difficult to write unit tests for. (Is there even a concept of a test that passes if if fails to compile or fails with an assertion in the boost testing framework?) I suppose I could mangle the interface to ensure that the user has nothing to invoke the API calls in question unless the transaction is in-progress, but that generally requires a custom "lock" interface for my RAII implementation that makes the API more complex to grasp. -- Jon Biggar jon(a)biggar.org

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[release] 1.66.0 closing for beta tomorrow
by Daniel James 13 Nov '17

13 Nov '17

Hi, I'll close the master branch for the beta release tomorrow. Sorry we've been quiet about the release and that this is a bit short notice. If you haven't written your release notes yet, you can add them to: https://github.com/boostorg/website/blob/master/feed/history/boost_1_66_0.q… Use the pencil icon at the top right of the code to edit it, or you can mail your notes to me, and I'll add them. thanks, Daniel

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[release][1.66.0] Permission to merge Hana
by Louis Dionne 12 Nov '17

12 Nov '17

Hi, Being at a C++ meeting all week, I did not see the release coming and the email in time. None of the changes to Hana have been merged to master, and I'd like to get them in for the release. Can I merge them, or should I wait until after the beta? Thanks and apologies for the untimeliness, Louis -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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[release][1.66.0] Permission to merge Predef.
by Rene Rivera 10 Nov '17

10 Nov '17

Some late fixes for Predef came in over the past two days: < https://github.com/boostorg/predef/commit/4a230ebe853980e27e7fb7cb36605fd6c… > < https://github.com/boostorg/predef/commit/74f88005cc2227b4f8fd4d640daae18c2… > < https://github.com/boostorg/predef/commit/5e8f5d5a4b9df640ffaeaf51e89c83e28… > Can I merge those to master for the beta? -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net

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Seeking endorsement for the reflection library (PFR)
by Antony Polukhin 10 Nov '17

10 Nov '17

Hello, PFR is a C++14 library that provides tuple-like methods for aggregate initializables. Library has a set of predefined operators and useful functions for everyday use. Works with user-defined types without any macro or boilerplate code. Library: https://github.com/apolukhin/magic_get Docs: http://apolukhin.github.io/magic_get/ Boost Library Incubator: http://blincubator.com/bi_library/pfr-pod-flat-reflection/?gform_post_id=16… Seeking for some endorsement, as per http://www.boost.org/development/submissions.html Library changes since last mail: * Now works on latest MSVC in C++17 mode * C++14 limitations in reflection were significantly relaxed * Removed UB (no more reinterpret casting of unrelated types!) * Thaler Benedek was approved as a review manager for the library. Boost libraries that may benefit from PFR: * Convert - for out-of-the-box conversions of user types * Hana - for using user types instead of tuples * Intrusive - for reusing unused bits in user provided types * Serialization - for out-of-the-box serialization of user types * Spirit - for putting rule results into user provided types without Phoenix or Fusion macro * Test - for outputting content of user provided types * TypeTraits - for traits like has_unique_object_representations in C++14 -- Best regards, Antony Polukhin

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A GUI Library
by jinhao 09 Nov '17

09 Nov '17

Hi, all I am developing a GUI library, it takes aim at easy-to-use and portable library for modern C++ methods. The project at http://stdex.sourceforge.net A git repository at http://nanapro.codeplex.com A brief at http://nanaproject.wordpress.com/2011/12/16/preliminary-study-of-nana-c-lib… Is there any interest in this library? Regards Jinhao

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[devector] optimum growing/insertion policy
by Joaquin M López Muñoz 08 Nov '17

08 Nov '17

Hi, Much an worthy discussion has taken place with respect to growing and insertion policies of boost::double_ended::devector. I think I can justify what the optimum policy is when the overall goal is to minimize number of element movements. What follows is *not* a formal optimality proof, though it's my hunch one could be provided relatively easily. Assumptions * The cost of allocating new memory is negligible when compared to the cost of moving elements around (either intra-buffer or when migrating to a new buffer); so, the growing/insertion policy should focus on minimizing number of elements moved. This implies fully occupying free space before reallocation is *not* the primary goal of the growing/insertion policy. * For the purposes of our discussion, we consider an ever-growing devector without intervening erasures --erasures can be accomodated later as we will see. * Element insertion is modelled as a process where each new insertion happens at a random position within the current devector. The minimal characterization (i.e. its 1st moment in stochastic process theory terminology) is just the percentage R of insertions that happen within the right half of the devector --we call these *right insertions*; left insertions happen then with a frequency L=1-R. push_back is a right insertion, push_front a left insertion. Facts * When a right insertion arrives, if there's free back capacity the optimum insertion policy is to shift elements to the right, as this involves fewer movements than the other way around. The symmetrical applies for left insertions. * If a right insertion at position N arrives and there's no free back capacity (but there is free front capacity), we have only two options: A. Reallocate to get back free capacity. B. Shift elements to the left. The key observation here is that A is cheaper in the long run: as the scenario is one of an ever-growing sequence, reallocation will happen eventually and we can just amortize it in our analysis, so reallocating early saves us the extra movements incurred when left shifting on a right insertion, namely N - (size()-N) = 2*N - size() movements. In fact, we save more than that as insertion is done simultaneously with reallocation, hence no shifting occurs additionally to the (amortized) reallocation cost. All this analysis applies symmetrically to left insertions, of course. * The optimum growing policy is that which maximizes the probability that *both* front and back free capacities get exhausted at the same time. With our 1st moment characterization of the insertion random process, this implies that when reallocating a percentage R of the new space should be devoted to the right side, and a percentage L to the left side. Description of resulting policy * Fix the growing factor to G (this can be 1.5 or 2 or anything greater than one, the actual figure is orthogonal to the discussion). * Maintain a counter right_ of right insertions that gets incremented when a right insertion occurs and *decremented* when an erasure is issued past the middle of the devector. * Right insertions trigger right shifting except when there's no back free capacity, in which case a reallocation is performed. * Left insertions trigger left shifting except when there's no front free capacity, in which case a reallocation is performed. * Reallocation reserves space for G*size() elements: of the resulting G*size()-size() free space, a fraction right_/size() is devoted to back free capacity, the rest to front free capacity. In practice, we may want to keep some minimum space at each end as determined by some empirical threshold. And that's it. Comments welcome. Joaquín M López Muñoz

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Including a system link library for every test, but only on mingw-w64 builds?
by James E. King, III 08 Nov '17

08 Nov '17

Is BOOST_AUTO_LINK supposed to work on mingw-w64 builds with gcc? I'm guessing not since I believe this is a MSVC concept, so I am looking for a bjam recipe that will allow me to add the link library bcrypt.lib to all of the tests in a project's test directory if the build is on a windows system and not using msvc toolset. Are these any examples out there? Thanks, Jim

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[type_traits] is_nothrow_move_constructible gives false positive on GCC 4.7
by Andrzej Krzemienski 08 Nov '17

08 Nov '17

Hi, It seems that boost::is_nothrow_move_constructible sometimes gives false positives on GCC 4.7. See the Git issue for details: https://github.com/boostorg/type_traits/issues/56 Regards, &rzej;

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