May 2016 - Boost - lists.preview.boost.org

New library? CallableTraits
by Barrett Adair 01 Jul '16

01 Jul '16

I posted about this a month ago, but I did not receive much response. Since then, I added an extended example use case, and I added a documentation section [1] that compares CallableTraits and Boost.FunctionTypes. I received some positive feedback this week in Aspen, and r/cpp also seemed to respond well [2], so I thought I'd give this another shot. Here are my questions for you: 1. Is there any interest in reviewing a future version of this for inclusion in Boost? 2. If so, does this belong in its own library, or should it be incorporated into Boost.TypeTraits or something similar? 3. What you like to see added, removed, renamed, or redesigned? I'd say CallableTraits is about 85% finished. Here's what's left: * Add INVOKE semantics to a couple of things for consistency (arity, etc) * Remove unused/undocumented code * Account for transaction_safe and C++17 noexcept * Finish/test the calling convention features * Finish/update the reference documentation * Write even more tests Cheers, Barrett [1] http://badair.github.io/callable_traits/doc/html/index.html#callable_traits… [2] https://www.reddit.com/r/cpp/comments/4ffmfs/callabletraits_never_write_ano… GitHub: https://github.com/badair/callable_traits Documentation from the top: http://badair.github.io/callable_traits/doc/html/index.html (reference section under construction)

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Pimpl Again?
by Vladimir Batov 10 Jun '16

10 Jun '16

Don't laugh but it is only fairly recently at work that I managed to move all our supported platforms to C++11. So, then, I started moving our code to C++11 (what a delight!) and stumbled upon my old pimpl which is used quite a bit around my workplace for all its good properties... :-) Now C++11-ed piml turned out to be very small and very basic. So basic it felt it did not have the right to exist. Still, it encapsulates and enforces the "proper" pimpl properties and behavior, reduces implementation minutia and offers a recognizable deployment pattern (helps other people reading the code). Over the years IMO the technique has been proven as legitimate and useful, a basic but important building block... rather than a curiosity item. Unfortunately, despite many articles and a few Sutter's GotWs about it there is nothing ready-to-go like std::unique_ptr. I feel that pimpl and its deployment pattern need to be codified, described, "standardized" and in our toolboxes to stop/avoid everyone re-inventing the pimpl and making the same mistakes. IMO Boost is best positioned for that. Do you think we might review what I've got and/or maybe collectively come up with something better... It's no MPL or Hana but as std::unique_ptr it's one of the first "little things" I personally reach out for in my everyday work. IMO having pimpl in Boost would save quite a few hours of frustration for many. Thoughts? No pressure. I am easy either way. :-) https://github.com/yet-another-user/pimpl Docs are freshened up but still somewhat out of date. Apologies.

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[announcement] GitHub permission changes
by Daniel Pfeifer 03 Jun '16

03 Jun '16

Hi all, GitHub finally allows us to set permissions on the level of granularity that we always wanted. When we moved to GitHub, we received many request like "can I please get admin rights to my repository?" We wanted to do that, but it just was not possible. As a workaround, we have created a team per repository and many of those teams had just one member. That way, we could at least give you write access to individual repositories. Not quite what you requested, but at least something. Anyway, it is now possible to set permissions on a per repository level. I have started to delete the teams with a single member and added the member as the owner of the repository. How do those changes affect you? As the owner of a repository you have write access as before, but you can also add collaborators, modify the repository descriptions, enable/disable issue tracking and wiki, and so forth. I will continue this cleanup soon, but I need your input. For teams with multiple members, I don't know whether you want to share ownership or whether you prefer to have a single owner and additional contributors. Please create new issues for that matter: https://github.com/boostorg/admin/issues Cheers, Daniel

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Boost.Fiber mini-review May 23 - June 1
by Nat Goodspeed 02 Jun '16

02 Jun '16

Hi all, The Boost.Fiber candidate library by Oliver Kowalke begins a mini-review today, Monday May 23, which will close Wednesday June 1. It was last reviewed in September 2015; the verdict at that time was "not yet." Oliver has been working steadily to address review comments and to improve the library in other ways, and has brought the library back for mini-review. The updated documentation is here: http://olk.github.io/libs/fiber/doc/html/index.html The code is on the master branch of this repository: https://github.com/olk/boost-fiber/tree/master I believe it is Oliver's intention to respond to review feedback on the develop branch, leaving the master branch stable during the review. I will monitor reviews and discussion on both the boost-users@ list and the boost@ developers' list. Please include at least "fiber" and "review" in the subject line of your mail, e.g. by replying to this message. (Please reply to only ONE list, however.) I will also check the Boost Library Incubator for Fiber reviews: http://rrsd.com/blincubator.com/bi_library/fiber/?gform_post_id=859 though I check that less frequently than email. Please do remember to state in your review whether you think the library should be accepted as a Boost library. Thank you for your interest and your feedback! ----------------------------------------------------- Here follows a synopsis of issues raised during the September 2015 review: Cross-thread fiber migration: Evidently the community strongly desires the ability to transfer a suspended fiber from one thread to another. Now supported, with documentation. Cross-thread migration support implies a requirement to document the thread safety requirements of the customization API. Addressed. Standard required timing specifications: meet (30.2.4 Timing specifications [thread.req.timing]). Addressed. Adapt one or more existing test suites for thread facilities to validate the correctness of the Fiber library's synchronization constructs. The requester clarified in private mail that I misstated his suggestion: he wanted Oliver to review one or more such test suites to discover the kinds of issues that can arise with thread synchronization constructs. He has professed himself satisfied with the current state of the Fiber library's synchronization constructs. std::chrono support: ensure that wait_until() can accept any supported time_point specialization. Addressed. C++11 compatibility. Addressed. Document that this_fiber::yield() (et al.) are valid from main(), or in general from a thread function, as well as from explicitly-launched fibers. Addressed. Make shared_state lock requirements explicit: for example, make mark_ready_and_notify_() accept a std::unique_lock<>& (or &&) to force its caller to provide one. Addressed. Avoid holding mutex during condition_variable::notify_*() calls. Addressed. packaged_task must not decay-copy its task arguments. Addressed. Align fibers::async() signature, result description and invoke_helper implementation with std::async(). Avoid returning std::move(...). Addressed. Wait list implementation: try an intrusive linked list of fiber_context objects. Addressed. Avoid sleeping thread when no fibers are ready -- block on external event. Better handling of waiting tasks (decentralized wait queues?). Addressed. Optimization to resume awakened fiber on the thread that awakens it. Hooks provided. Template redundancy: eliminate duplication between specializations for T, T& and void. The future, shared_future, shared_state, promise and task_object templates were specifically cited. Addressed. Leverage predicate-based condition::wait() overload internally. Addressed. Nested schedulers: make schedulers be schedulable entities themselves. Not implemented. Improve robustness of `promise' handling in Asynchronous Callbacks documentation. Avoid overconfident remarks about it. Addressed. Fix Note overstating the requirements on condition_variable::wait(). Addressed.

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[optional] using name boost::in_place -- need your opinion/advice
by Andrzej Krzemienski 30 May '16

30 May '16

Hi Everyone, I have stumbled upon a problem that I do not know how to address. I would like to seek an advice from the people in this list. I am trying to make boost::optional resemble std::optional (where it is reasonably easy to achieve). std::optional has this nice and useful "placement" constructor: std::optional<std::mutex> m {std::in_place}; std::in_place is a tag type, that instructs std::optional to create an object using placement-new syntax, from the provided arguments (zero in the example), without incurring any move construction. I cannot easily copy 1-to-1 this solution, because in namespace boost name in_place is reserved for the in-place factories: http://www.boost.org/doc/libs/1_61_0/libs/utility/in_place_factories.html I could simply go with a different name for a tag, but something tells me it would introduce an unnecessary complications for users that want to migrate from one optional to another. I could hack in-place factories so that they can also be used as a tag, although, I am not sure it is doable in a type-safe manner, and if it would not confuse people to have this boost::in_place do a number of different things. I could use a different namespace, but again, this might look surprising.I am a bit torn. I wonder if anyone here needed to face a similar problem, and if you can think of an elegant solution. Thanks, &rzej

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[Boost.Test][Boot.Timer v2] header only boost.test conflicts with Boot.Timer V2
by Tan, Tom (Shanghai) 30 May '16

30 May '16

This following simple snippet would yield an error with visual studio 2015 for both boost1.60.61: boost/timer/timer.hpp(32): error C2757: 'timer': a symbol with this name already exists and therefore this name cannot be used as a namespace name // compiled with cl.exe /EHsc #define BOOST_TEST_MODULE test #include <boost/test/included/unit_test.hpp> #include <boost/timer/timer.hpp> The following variants are ok // compiled with cl.exe /EHsc #define BOOST_TEST_MODULE test #include <boost/test/unit_test.hpp> #include <boost/timer/timer.hpp> Or // compiled with cl.exe /EHsc #define BOOST_TEST_MODULE test #include <boost/test/included/unit_test.hpp> #include <boost/timer.hpp> It looks like Boost.Test is relying on boost.timer v1, which is deprecated in documentation and conflict with V2.

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[boost.timer v2] auto_cpu_timer does not compile
by Tan, Tom (Shanghai) 29 May '16

29 May '16

This following snippet generates an error with VS2015 both fo 1.60&1.61: libboost_timer-vc140-mt-s-1_61.lib(cpu_timer.obj) : error LNK2019: unresolved external symbol "public: static class boost::chrono::time_point<class boost::chrono::steady_clock,class boost::chrono::duration<__int64,class boost::ratio<1,1000000000> > > __cdecl boost::chrono::steady_clock::now(void)" (?now@steady_clock@chrono@boost@@SA?AV?$time_point@Vsteady_clock@chrono@boost@@V?$duration@_JV?$ratio@$00$0DLJKMKAA@@boost@@@23@@23@XZ) referenced in function "public: struct boost::timer::cpu_times __cdecl boost::timer::cpu_timer::elapsed(void)const " (?elapsed@cpu_timer@timer@boost@@QEBA?AUcpu_times@23@XZ) // compile with cl.exe /EHSc #include <boost/timer/timer.hpp> int main() { boost::timer::auto_cpu_timer t; } What's interesting is that uncommenting line #14 in file boost/timer/timer.hpp would get rid of this error. - Why is there such a line but commented out there? - Is there a better way to get it through without modifying this file - the binary is downloaded from sourceforge, not a custom build. - Thanks.

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Re: [boost] Boost.Fiber mini-review May 23 - June 1
by Bjorn Reese 28 May '16

28 May '16

On 05/23/2016 06:20 PM, Nat Goodspeed wrote: > Please do remember to state in your review whether you think the > library should be accepted as a Boost library. Yes, I vote for unconditional acceptance of Boost.Fiber. I did not participate in the formal review (due to time constraints), so I am not going to address the individual issues. I happened to have studied Boost.Fiber recently because I came across limitations of the inter-coroutine interaction in Boost.Coroutine, and Boost.Fiber addresses these limitations rather nicely. I especially like the message passing channels, which makes Boost.Fiber an obvious choice for building a coroutine-based actor framework. The only finding I have is that several Boost.Fiber headers include detail headers from Boost.Context. While this is not a problem per se (because Oliver is the maintainer of both libraries), it may be an idea to consider if these detail headers should be made public.

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[iterator] strided, recursive variants
by Jeremy Murphy 28 May '16

28 May '16

Dear Boosters, I was wondering why a strided iterator has not made it into the Boost.Iterator library? There is a strided range in Boost.Range based on a private implementation of such an iterator, and Boost.Compute has their own implementation too. Just an untied loose end? On a related note, what about variants of such iterators that work in recursive algorithms? That is, if you stride a strided iterator, existing implementations will keep nesting the stride type, which the compiler fails to do recursively because there is no stopping criterion. So I wrote a variant of strided iterator that when you stride a strided iterator, it just multiplies the two strides together and takes the base pointer type from the original strided iterator. I assume some of the other iterator adaptors are limited in the same way. Anyway, it's no big deal to me, but I just thought I'd canvas whether that's something people (especially the maintainers) are interested in? Cheers. Jeremy

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compiling mysql-5.7.12, cannot use DTRACE
by Mariano Apilado 26 May '16

26 May '16

Hi, I get the following error when compiling mysql-5.7.12 on Nexenta 4.0.4 OS ( Formerly known as Open Solaris / Illumos ). To temporarily bypass this problem, I chose not to use DTRACE with the compiler options. However, it should be fixed to use DTRACE. # cmake -DENABLE_DTRACE=0 Thanks and Regards,Mariano [ 15%] Linking CXX static library libmysys_ssl.a cd /usr/local/mysql-5.7.12/mysys_ssl && /usr/local/bin/cmake -P CMakeFiles/mysys_ssl.dir/cmake_clean_target.cmake cd /usr/local/mysql-5.7.12/mysys_ssl/CMakeFiles/mysys_ssl.dir && /usr/local/bin/cmake -DDTRACE=/usr/sbin/dtrace -DOUTFILE=/usr/local/mysql-5.7.12/mysys_ssl/CMakeFiles/mysys_ssl.dir/mysys_ssl_dtrace.o -DDFILE=/usr/local/mysql-5.7.12/include/probes_mysql.d -DDTRACE_FLAGS=-64 -DDIRS=. -DTYPE=STATIC_LIBRARY -P /usr/local/mysql-5.7.12/cmake/dtrace_prelink.cmake dtrace: failed to link script /usr/local/mysql-5.7.12/include/probes_mysql.d: No probe sites found for declared provider cd /usr/local/mysql-5.7.12/mysys_ssl && /usr/local/bin/cmake -E cmake_link_script CMakeFiles/mysys_ssl.dir/link.txt --verbose=1 /usr/bin/ar qc libmysys_ssl.a CMakeFiles/mysys_ssl.dir/crypt_genhash_impl.cc.o CMakeFiles/mysys_ssl.dir/mf_tempdir.cc.o CMakeFiles/mysys_ssl.dir/my_default.cc.o CMakeFiles/mysys_ssl.dir/my_getopt.cc.o CMakeFiles/mysys_ssl.dir/my_aes.cc.o CMakeFiles/mysys_ssl.dir/my_sha1.cc.o CMakeFiles/mysys_ssl.dir/my_sha2.cc.o CMakeFiles/mysys_ssl.dir/my_md5.cc.o CMakeFiles/mysys_ssl.dir/my_rnd.cc.o CMakeFiles/mysys_ssl.dir/my_murmur3.cc.o CMakeFiles/mysys_ssl.dir/my_aes_yassl.cc.o /usr/bin/ranlib libmysys_ssl.a cd /usr/local/mysql-5.7.12/mysys_ssl && /usr/bin/ar r /usr/local/mysql-5.7.12/mysys_ssl/libmysys_ssl.a /usr/local/mysql-5.7.12/mysys_ssl/CMakeFiles/mysys_ssl.dir/mysys_ssl_dtrace.o ar: cannot open /usr/local/mysql-5.7.12/mysys_ssl/CMakeFiles/mysys_ssl.dir/mysys_ssl_dtrace.o: No such file or directory ar: /usr/local/mysql-5.7.12/mysys_ssl/CMakeFiles/mysys_ssl.dir/mysys_ssl_dtrace.o not found gmake[2]: *** [mysys_ssl/libmysys_ssl.a] Error 1 gmake[2]: *** Deleting file `mysys_ssl/libmysys_ssl.a' gmake[2]: Leaving directory `/usr/local/mysql-5.7.12' gmake[1]: *** [mysys_ssl/CMakeFiles/mysys_ssl.dir/all] Error 2 gmake[1]: Leaving directory `/usr/local/mysql-5.7.12’ gmake: *** [all] Error 2

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