March 2015 - Boost - lists.boost.org

Release deadlines
by Marshall Clow 30 Mar '15

30 Mar '15

Just a reminder that we’re coming up on a release; and if you have changes that you want to see in the release (I know *I* do), you should get them in ASAP. Check them into develop, and then, once the tests have cycled successfully, merge them to master. Please do not merge anything to master w/o permission from the release managers after the start of April (11:59 PM next Tuesday PDT). Also, if you know of problems with the current state of the master branch that would preclude releasing it, please let us know (preferably *before* next Wednesday). Thanks for your help with the releases. — Marshall & the rest of the release managers.

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[serialization] Passing literals to oarchive
by Bjorn Reese 30 Mar '15

30 Mar '15

Currently we cannot pass literals directly to an oarchive like this: oarchive << 42; since compilation fails in interface_oarchive.hpp, as the operator<< only takes parameters by reference. We can remedy this by changing operator<< to take the parameter by const-ref instead, as show below. Is there any reason not to do this? --- a/include/boost/archive/detail/interface_oarchive.hpp +++ b/include/boost/archive/detail/interface_oarchive.hpp @@ -59,7 +59,7 @@ public: } template<class T> - Archive & operator<<(T & t){ + Archive & operator<<(const T & t){ this->This()->save_override(t, 0); return * this->This(); }

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[mpl] Is BOOST_MPL_PP_TOKEN_EQUAL publicly usable ?
by Damien Buhl 30 Mar '15

30 Mar '15

Dear Boost.MPL developers, I was coming up to something really similar to BOOST_MPL_PP_TOKEN_EQUAL ( http://www.boost.org/doc/libs/1_57_0/boost/mpl/aux_/preprocessor/token_equa… ) in Boost.Fusion to fix warnings that my changes generate in MSVC 8 ( As discussed on this list as *[boost] MSVC warnings for BOOST_PP_IS_EMPTY in Boost.Phoenix* ) Instead of having a second implementation of the same macro within Boost.Fusion, is it ok if I use BOOST_MPL_PP_TOKEN_EQUAL from MPL ? I'm asking this because it isn't documented anywhere and is in mpl/include/boost/mpl/aux_/preprocessor/token_equal.hpp which sounds like a private header. Possibly there are reasons for not being documented ? Cheers, -- Damien Buhl

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Re: [boost] [Locale] Boost.Locale cannot Run in Visual Studio 2010
by Artyom Beilis 30 Mar '15

30 Mar '15

> >I have been trying to learn Boost.Locale Module. Consider this >http://www.boost.org/doc/libs/1_55_0/libs/locale/doc/html/conversions_8cpp-… >example. The code gets successfully compiled but when I try to run it, it >gives the error > >Unhandled exception at 0x74d34b32 in LearningCPP.exe: Microsoft C++ >exception: std::bad_cast at memory location 0x00a6fa48.. > >I have attached the stack-trace of the program also. Here it is: > > [snip] > > Did anyone faced this issue when using Boost.Locale in Visual Studio 2010? > If so, how do I resolve this issue? 1. Do you use latest version of MSVC or public beta (there was facet related bug there)2. Make sure you don't mix debug and release code (which can be very likely stuff there) on both boost and its dependencies (icu if you use one) Artyom Beilis -------------- CppCMS - C++ Web Framework: http://cppcms.com/ CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/

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[GSOC] Request for proposal review and feedback
by Divyansh Gupta 30 Mar '15

30 Mar '15

Hi BOOST, I had submitted my proposal for the enhanced vector and deque project on 17th March, but I haven't received any comments yet. It would be great if I could get some feedback on the proposal, so that I can make any necessary changes while that's allowed. Thanks a lot. Regards, Divyansh Gupta PS- Here's the link to the proposal: https://www.google-melange.com/gsoc/proposal/review/student/google/gsoc2015…

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[thread] Alternate future implementation and future islands.
by Giovanni Piero Deretta 29 Mar '15

29 Mar '15

[cc'ing a few of the participants of the old thread] Hi All, Back in January, there was an interesting long thread about the problem of interoperation between futures of different libraries and the ability wait for heterogeneous futures. Different solutions were discussed like standardizing the future shared state or having an unified kernel wait object. I just wanted to share my attempt on a solution on the problem. The code can be found at https://github.com/gpderetta/libtask/blob/master/future.hpp (other interesting files are shared_future.hpp event.hpp and tests/future_test.cpp). It is an implementation a subset of the current boost and std future interface. In particular it has promise, future, shared_future, future::then, wait_any, wait_all. Most important missing piece are timed waits (for lack of, ahem, time, but should be easy to implement). The implementation requires c++14 and is only lightly tested, it should be treated as a proof of concept, not production-ready code. A few key design points: * The wait strategy is not part of the future implementation (although a default is provided). future::get, future::wait, wait_all and wait_any are parametrized by the wait strategy. * The design aims to streamline and make as fast as possible future and promise at the cost of a slower shared_future (although there is room for improvement). * The wait strategy only deals with 'event' objects, which act as a bridge between the future and the promise. The event object is really my the core of my contribution; it can be thought of as the essence of future<void>::then; alternatively it can be seen as a pure user space synchronization primitive. Other features of this implementation: * Other than in the blocking strategy itself, the future and promise implementation have no sources of blocking (no mutexes, not even spin locks). * The shared state is not reference counted. To demonstrate the generality of the waiting concept, I have implemented a few waiter objects. * cv_waiter: this is simply a waiter on top of an std::mutex + cond var. * futex_waiter (linux): an atomic counter + a futex, possibly more efficient than the cv_waiter * sem_waiter (posix): a waiter implemented on top of a posix semaphore. More portable than the futex waiter and possibly more efficient than the cv_waiter * fd_waiter(linux, possibly posix): a waiter implemented on top of linux eventfd (for portability it can also be implemented on top of a pipe); you can use select with futures! * task_waiter: a completely userspace based coroutine waiter which switches to another coroutine on wait and resumes the original coroutine on signal. * scheduler_waiter: another coroutine based waiter, but on top of an userspace task scheduler. On wait switch to the next ready task, on signal enqueue the waiting task to the back of the ready queue. I know that there is a plan to reimplement a new version of boost::threads, hopefully this implementation can contribute a few ideas. HTH, -- gpd

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[vmd] Updated VMD library
by Edward Diener 28 Mar '15

28 Mar '15

I have updated the VMD library which has been accepted into Boost based on the reviews and comments of others. The macro interfaces have been simplified and redesigned for easier use and the documentation has been updated to provide more examples and samples of using VMD in code. The library is currently at https://github.com/eldiener/variadic_macro_data. The latest library code is now on the 'master' branch and the code that was reviewed is on the 'Version17' branch. The VMD library is a library of variadic macros which enhance the functionality in the Boost preprocessor library ( Boost PP ). The main focus of the library is the parsing/identifying of a subset of C++ preprocessor data types and of all Boost PP data types. This allows enhanced preprocessor metaprogramming based on the type of macro input. The library has been successfully tested on gcc 4.3.0 on up, VC++ 8 on up, clang 3.3 on up, and Intel 12.1 on up. The library has been tested on Windows and Linux. Comments, questions, bug reports are welcome.

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sun toolset buggy and outdated?
by John Maddock 28 Mar '15

28 Mar '15

I'm trying to test the new Oracle-solaris compiler but I'm running into Boost.Build issues. First off what looks like a bug, if I build with with b2 stdlib=native Then I *still* get stlport You can easily reproduce this on another platform with: cd libs/config/test ../../../b2 config_info toolset=sun stdlib=native -n -d2 which yields: sun.compile.c++ ..\..\..\bin.v2\libs\config\test\config_info.test\sun\debug\stdlib-sun-stlport\config_info.obj "CC" +d -library=stlport4 -g -erroff=%none -KPIC -DBOOST_ALL_NO_LIB=1 -I"..\..\.." -c -o "..\..\..\bin.v2\libs\config\test\config_info.test\sun\debug\stdlib-sun-stlport\config_info.obj" "config_info.cpp" Now for the outdated part: the oracle compiler (12.4) now supports three std lib options: 1) The default - I can't make this work in C++03 mode, but it's the only option that does work in C++11 mode (where it appears to be a recent GNU libstdc++ version). 2) STLPort - only works in C++03 mode. 3) Apache - only works in C++03 mode. So ideally we would probably have: stdlib=stlport, sets -library=stlport4 for both compile and link. stdlib=apache, sets -library=stdcxx4 for both compile and link stdlib=native, sets -std=c++11 for both compile and link. And yes I realise we're mixing up two different features here, but as they can't be mixed and matched anyway it at least gets things working. I guess the toolset should be renamed either "oracle" or "solaris" as well? If anyone has any ideas how to patch the toolset, I have a working virtual machine to test on (or you can do as I did and download a pre-build VirtualBox machine). Thanks in advance, John.

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[gsoc15] Please help rank GSoC 2015 student projects
by Niall Douglas 28 Mar '15

28 Mar '15

Dear Boost Community, The Google Summer of Code 2015 proposals for Boost are in, and we would deeply appreciate the community's help in ranking the proposals according to merit before the 6th of April. To vote, the process is easy: 1. Go to this page https://www.google-melange.com/gsoc/homepage/google/gsoc2015 and click the "Log in" button under Mentors and Administrators. 2. Now click "Create Profile" on the same page. Note that even if you registered last year, you must register again in 2015. Fill in the form. Note that after submitting it drops you at "Edit Profile", which is confusing. 3. Click "My Dashboard", then "Connect with organisations". 4. Choose "Boost C++ Libraries". 5. In the message box, write this: "I am a member of the Boost community and the email(s) I normally post to boost mailing lists with is <email>" filling in the email address(es) you normally use to post to boost mailing lists. This lets us verify that you are indeed a long standing member of the Boost community. 6. Once we approve your request, you will get an email with the subject "Welcome as organisation member". You can now return to the Dashboard on the GSoC website where there will be a new item "Proposals". 7. Work your way through as many of the 33 proposals as you can. You can score them using the stars at the bottom of each proposal page, taking care to read any comments by the mentors and students if present. PLEASE try to rank some of the lowest scored proposals, every year we get a lot of people who only rank the top five and don't bother with the rest. Try to score on the priority basis of: (i) ability to write quality C++, using the programming competency test or samples of programming the student supplied. (ii) proposal quality and your best estimate of the student's understanding of how best to solve the problem at hand. Bear in mind a gifted programmer with a strong work ethic but poor English may appear to not understand the problem as well as native English speakers, this is why we have asked for examples of their programming competency. (iii) if the student came early to the mailing lists to ask for help writing the proposal (the mentors who helped them with their proposals have usually indicated this in the private comments). (iv) usefulness/appropriateness of the feature or work being proposed. Remember a good GSoC is more about getting promising new engineers into Boost and C++ than necessarily getting code to pass Boost peer review in a single summer. 8. Optional: If a proposal looks especially great to you and you feel able to mentor a student this year, please slide the "wish to mentor" button. Just because a proposal already has willing mentors does NOT mean you should not add yourself - if you can substitute for an existing mentor, that may mean we use that mentor for another proposal. As you know, Google Summer of Code is usually worth $42,000 - $48,000 to Boost each year, and a successful GSoC raises our visibility and reputation in the wider open source community. Our thanks to you in advance for taking the time to vote. Niall Douglas Boris Schäling --- Boost C++ Libraries Google Summer of Code 2015 admin https://svn.boost.org/trac/boost/wiki/SoC2015

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[SmartPointers] Determine interest in a new pointer wrapper class "flex_ptr"
by Jakob Riedle 27 Mar '15

27 Mar '15

Hello Boost Community, In the last few weeks, I heavily felt the lack of boost not having a more lightweight solution to a "not-necessarily-owning" pointer-wrapper than shared_ptr. shared_ptr is quite slow in the context that I need it to work. Furthermore it always is owning, even though ownership is shared in between instances. This is unhelpful, if you have an std::list of both non-owning and owning pointers. Hence, if you do not want to use shared_ptr all over your project, or especially want to interact with C, you need a not-necessarily-owning pointer-wrapper. This is why I collected some ideas on how to improve the situation. I came up with a little class named 'flex_ptr', that can hold both strong and weak references (therefore the name 'flexible', but it can also be 'the name of whatever proves itself to be good ...'). It keeps track of whether the held pointer is strong or weak. The Class doesn't need reference counting, since an Instance either is owning, or non-owning. Ownership is transferred between Instances using the default Move/Copy behavior. By Default the Constructor takes a pointer and treats it as a weak one. This is required, since this class aims on being used only at places, that are ought to be able to but not necessarily own objects. (Excuse me for the long sentence) A flex_ptr instance holding a strong pointer is created using a static non-member method named 'make_owning_flex', which accepts an rvalue pointer. As a result, it is not required to use the class at every single pointer occurrences in the project, but only at places, where the programmer wants to allow but not force strong references. The flex_ptr class is easily integrated into existing code using unique_ and shared_ptr's: One could think of - a constructor accepting a const lvalue reference unique_ptr, creating a (flex_ptr-instance holding a) weak reference, - a constructor accepting an rvalue unique_ptr, creating a strong pointer, that is owning an object it received from unique_ptr, - as well as a constructor taking a const lvalue reference shared_ptr, creating a weak pointer. Résumé: This pattern allows outright memory management, it uses less memory than shared_ptr (because no reference counting object required), therefore is faster, allows well-defined interactions similar to unique_ptr (especially at interaction with C) and thus fills a yet unclosed gap in the boost library as well as the Standard. Since this is (only) my personal opinion, I'd like to see how people feel about this 'gap' and think about this addition in the library (however the pattern may be implemented in the end). Regards, Jakob Riedle

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