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

GSOC 2016
by Boldy Happy 18 Feb '16

18 Feb '16

Hello!I would like to know if Boost is participating in GSOC 2016.Please excuse if me if I made a mistake by sending this kind of email as I am just a beginner. Thanks in advance!

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Interest in double ended containers
by Benedek Thaler 18 Feb '16

18 Feb '16

Dear Boost, I'd like to draw attention to my double_ended library, founded by GSoC 2015. It provides two containers, briefly described below. Given there's interest, I'd like to propose this library later. Documentation: http://erenon.hu/double_ended/ Source: https://github.com/erenon/double_ended Short overview: `devector` is a hybrid of the standard vector and deque containers, as well as the `small_vector` of Boost.Container. It offers cheap (amortized constant time) insertion at both the front and back ends, while also providing the regular features of `std::vector`, in particular the contiguous underlying memory. In contrast to the standard vector, however, `devector` offers greater control over its internals. Like `small_vector`, it can store elements internally without dynamically allocating memory. `batch_deque` is very similar to the standard `deque`, with a slight twist. It lets you specify its segment size: The size of the contiguous memory segments it uses to store its elements. This provides a consistent layout across platforms, and lets you iterate over the segments with batch operations. Thanks, Benedek

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[block_ptr] Use case bug
by Phil Bouchard 18 Feb '16

18 Feb '16

In trying to anticipate all possible use cases, I think I have found a bug. Please let me try to fix it, but this is not so simple so it'll take some time.

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[githelp]
by Rene Rivera 17 Feb '16

17 Feb '16

How can I find out what changes are not merged from develop to master, for all subrepos, but only changes I've made? -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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Removal of boost::basic_string_ref (in favor of basic_string_view)
by Marshall Clow 17 Feb '16

17 Feb '16

I have just removed boost::basic_string_ref from the develop branch, and updated the specializations to use basic_string_view. Code that uses boost::string_ref (and wstring_ref) should continue to work as before. The basic_string_view class better matches what the standards committee is doing and has WAY more constexpr support. I'll be watching the testbots for results, but I believe that the only part of boost that was using basic_string_ref was Boost.Log, and that was switched over to basic_string_view in December. -- Marshall

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Boost.Operators issue: polluting namespace of caller through argument-dependent lookup
by John M. Dlugosz 17 Feb '16

17 Feb '16

Here's the problem I ran into http://stackoverflow.com/questions/34449254/how-is-argument-dependent-looku… |usingstd::tr1::shared_ptr; ||usingstd::tr1::make_shared;| |shared_ptr<Dog>Gamma::knockout (constHotel&target){Eggsoftboiled (target.ID);softboiled.sequence ^=0x40000000;returnmake_shared<Dog>(softboiled,target.kin,Frank::myself());} | The arguments to the constructor passed through make_shared are of types |Able::Bravo::Charlie::Egg&,constuint32_t&,constFrank&| The use of make_shared is finding boost::make_shared as well as std::make_shared. The program doesn't use boost::shared_ptr and shouldn't need to know about it. It turns out that Frank is derived privately from boost::totally_ordered1 (and and Egg from boost::totally ordered). Some Boost header that's being used in this translation unit just happens to pull in Boost's shared_ptr stuff. It ends up effectively polluting the namespace of possible calls involving these types, thanks to argument-dependent lookup. Furthermore, which Boost headers include which will change from version to version. I have this problem show up much more in Boost 1.60 than I have in Boost 1.59. There is no easy way around it beyond qualifying the call make_shared, and I specifically want to avoid that so I don't litter the program with tr1's (this varies by compiler and version as to whether tr1 is required, prohibited, or optional, so I want it in one place.) I believe the proper thing to do, which is a very simple fix actually, is to define the mix-in classes like totally_ordered (and other things from Boost.Operators in particular) in a unique inner namespace, and then make aliases in the boost namespace where they are published as being found. namespace boost { *namespace inner_name_1 { * template<typename T, Typename U> partially_ordered { ⋯ }; // the entire guts of Boost.Operators can go here, I think. *} // end of inner isolating namespace** ** ** using inner_name_1::partially_ordered;* // etc. } This inner isolation technique should be SOP for any classes that are meant to be inherited from by user (non-Boost library) code. It would not hurt to also isolate classes that match the names of std library code, in general! This would, in general, prevent the libraries from interfering with each other and surprises popping up when using std components and pulling in Boost headers. —John ||

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remove cached feature checks
by Oliver Kowalke 17 Feb '16

17 Feb '16

Hi, how is it possible to remove the cached feature checks? Boost.Config Feature Check: cxx11_constexpr : no (cached) b2 -a toolset=clang cxxflags="-std=c++11" does not re-check the features. Oliver

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[block_ptr] 20% speed boost
by Phil Bouchard 17 Feb '16

17 Feb '16

> If I try out the latest modifications and I disable the threads then on > Linux I have: > > make: > auto_ptr: 2458626 ns > shared_ptr: 2685224 ns > block_ptr: 28300624 ns > > new: > auto_ptr: 2383605 ns > shared_ptr: 4992185 ns > block_ptr: 7979659 ns So I just added a specialization of the pool for GCC x86 and now block_ptr<> speeds up by 20%: make: auto_ptr: 2511658 ns shared_ptr: 2695469 ns block_ptr: 22547960 ns new: auto_ptr: 2369312 ns shared_ptr: 4991352 ns block_ptr: 6443925 ns Thanks, -Phil

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[Fit] Purpose and Use Cases
by Artyom Beilis 17 Feb '16

17 Feb '16

Hello, Before the formal review begins I would really like to understand the purpose of Boost.FIT It isn't clear to me from the documentation what are the real world use cases? What can't be done today (for example composition) with simple C++11 lambdas? I'd love to see several real world examples and use cases of Boost.FIT - because at least for me I don't really understand why it is useful. Artyom

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Re: [boost] [block_ptr] Request for a review manager
by Bjorn Reese 17 Feb '16

17 Feb '16

On 02/04/2016 03:02 AM, Phil Bouchard wrote: > On the other hand I code completed the deterministic block_ptr in 2011 > and I am wondering if there is anything I am missing to get it through > the review process because this is one of the most important subject in > computer science: > https://svn.boost.org/svn/boost/sandbox/block_ptr/libs/smart_ptr/doc/index.… Do you have any performance measurements comparing block_ptr<T> with shared_ptr<T>? Btw, in the overview section you claim that shared_ptr<T> has to manage counters when it is dereferenced. I am not entirely sure that is correct.

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Boost.Python gsoc project
by Barun Parruck 16 Feb '16

16 Feb '16

Hi! I'm a student looking to get involved with the open source through boost. I was looking through the gsoc projects, and the one involving Boost.python, by Stefan Seefeld piqued my interest! I was wondering what sort of student you'd be looking for for the project, more details about what the project would entail, and what sort of programming competency test I would have to pass.

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stupid github question
by Robert Ramey 16 Feb '16

16 Feb '16

I want to add a contributer to the serialization library - but I can't figure out how to do this on github. I believe this has something to do with the fact that the serialization library is a sub project. It shouldn't be a big deal as I see there are already 31 contributors on the list - many of whom I don't recognise. Robert Ramey

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Alternative remove, erase, and partition algorithms
by Brent Friedman 15 Feb '16

15 Feb '16

Hello, I'd like to propose the following for inclusion in Boost.Algorithm. *semistable_partition* partitions a range into 'good' and 'bad' elements, as partition. 'Good' elements maintain their order, while 'bad' elements are left in unspecified order. stable_partition has either linear additional storage or performs 3NlogN move operations, whereas semistable_partition has constant memory overhead and at most 3N move operations. Requires forward iterators. *unstable_remove ( _if )* removes elements from a range but without maintaining element order. Performs at most N/2 moves as compared to N for remove. Requires bidirectional iterators. *unstable_erase* erases an iterator or range from a container ( as vector::erase ) without maintaining element order. Intuitively, this fills in the hole created by the erase operation by moving elements from the end. Limited to containers with bidirectional iterators (possibly random-access). The following documents describe and explore these algorithms: https://groups.google.com/a/isocpp.org/forum/#!topic/sg14/2uwOmXWqa2E (unstable_erase, unstable_remove) https://iterator.wordpress.com/2016/01/31/algorithms_0/ (unstable_remove, semistable_partition) I have been pursuing standardization, but it seems like there is value in getting community experience with these algorithms first in order to make for easier justification. -Brent Friedman

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[block_ptr] Works on MSVC + Boost.Pool bug
by Phil Bouchard 15 Feb '16

15 Feb '16

It looks like I was able to fix a bug which makes it run correctly under MSVC 2015 Express. Although I do have a crash in the boost::pool: Project2.exe!boost::simple_segregated_storage<unsigned int>::try_malloc_n(void * & start, unsigned int n, unsigned int partition_size) Line 333 C++ Project2.exe!boost::simple_segregated_storage<unsigned int>::malloc_n(unsigned int n, unsigned int partition_size) Line 363 C++ Project2.exe!boost::pool<boost::default_user_allocator_new_delete>::ordered_malloc(unsigned int n) Line 801 C++ Project2.exe!boost::singleton_pool<boost::detail::bp::pool,1,boost::default_user_allocator_new_delete,boost::details::pool::null_mutex,32,0>::ordered_malloc(const unsigned int n) Line 149 C++ Project2.exe!boost::detail::bp::pool::allocate(unsigned int s) Line 148 C++ Project2.exe!boost::detail::bp::block<int>::operator new(unsigned int s) Line 283 C++ Project2.exe!boost::detail::bp::make_block<int,int>(const int & t0) Line 520 C++ > Project2.exe!main() Line 119 C++ When I try this example: https://github.com/philippeb8/block_ptr/blob/master/example/block_ptr_test2… Thanks, -Phil

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Re: [boost] [block_ptr] Request for a review manager
by Peter Dimov 15 Feb '16

15 Feb '16

> Phil Bouchard wrote: > > > I added the new repository with the right folder structure: > > https://github.com/philippeb8/block_ptr > > You should update this to work with the latest Boost, because currently > block_base is abstract as it doesn't implement > > virtual void * get_untyped_deleter() = 0; It also doesn't work with -DBOOST_DISABLE_THREADS, which makes it inconvenient to test as it requires Boost.Thread.

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[dll] dbghelp.hpp in detail/winapi
by Andrey Semashev 14 Feb '16

14 Feb '16

Hi, I've noticed that Boost.Dll provides boost/detail/winapi/dbghelp.hpp header. boost/detail/winapi is the directory of Boost.WinAPI submodule, and I generally don't expect anyone else putting his header in that directory. Could dbghelp.hpp be moved somewhere inside boost/dll?

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Re: [boost] expected/result/etc
by Emil Dotchevski 13 Feb '16

13 Feb '16

On Wed, Jan 27, 2016 at 10:49 PM, Michael Marcin <mike.marcin(a)gmail.com> wrote: > So looking a few of these libraries/proposals I have a few things I'm > interested in. > > - Is it at least as good as a simple hand-rolled solution? > - Can you transport error codes through layers without knowing specifics > of an error? > > For the second Niall's outcome/result handles very well I think. > std::error_code and std::exception_ptr transport is good enough for almost > any reasonable type agnostic error transport. > Have you considered using Boost Exception? It lets you add arbitrary data to exception objects, even after they have been thrown, regardless of their type -- see http://www.boost.org/doc/libs/release/libs/exception/doc/error_info.html. The general idea is to adopt a strategy where the exception objects are augmented with any, even platform-specific relevant data, which then the catch site can analyze to choose the correct handling. Cheers, Emil

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[type_traits] ICE with msvc-12.0
by Steven Watanabe 13 Feb '16

13 Feb '16

AMDG I'm getting boost\type_traits\common_type.hpp(43): fatal error C1001: An internal error has occurred in the compiler. (compiler file 'msc1.cpp', line 1325) To work around this problem, try simplifying or changing the program near the locations listed above. which makes this toolset basically unusable. Oddly enough, I don't see this error in the regression matrix. Does anyone know what's up with this? > cl Microsoft (R) C/C++ Optimizing Compiler Version 17.00.50727.1 for x86 Copyright (C) Microsoft Corporation. All rights reserved. scratch.cpp: #include <boost/type_traits/common_type.hpp> int main() { boost::type_traits::common_type<int, char, long>::type x = 0; } > cd libs/type_traits > git log commit 1f3a3a1553dc316ed002354dce3ba3f081b2e102 Author: jzmaddock Date: Wed Jan 13 10:50:22 2016 +0000 Fixes for older GCC versions, see issue 11904. ... > dir boost ... 02/25/2015 08:26 PM <JUNCTION> type_traits [...\libs\type_traits\include\boost\type_traits] ... In Christ, Steven Watanabe

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[regression] Winapi submodule tests missing
by Andrey Semashev 13 Feb '16

13 Feb '16

Hi, The winapi submodule tests are missing from the test matrix, although the status/Jamfile.v2 lists it. This is both on develop and master. Is there something I should do to make the tests appear?

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Re: [boost] expected/result/etc
by Giovanni Piero Deretta 13 Feb '16

13 Feb '16

On 12 Feb 2016 11:20 a.m., "Niall Douglas" <s_sourceforge(a)nedprod.com> wrote: [...]. > > LLVM, for the record, has implemented a very similar "universal" > exception handling mechanism which allows exception throws to > traverse language boundaries within LLVM, and my great hope is that > once LLVM becomes universal on POSIX platforms someone will go ahead > and replace signals with structured exception handling. As far as I know LLVM simply implements unwinding as mandates by the Itanium ABI, which is already the de facto standard on many unices. Is this what you are referring to? This is completely orthogonal with handling OS/machine exceptions (segfaults, division by zero, etc..). And with right compiler and flag there are ways to convert (synchronous) signals to exceptions. This actually required to support the semantics of languages other than the C family, like Java and Ada. Notably, it doesn't actually work with LLVM, but it does with gcc. -- gpd

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[filesystem] temp_directory_path and Android devices (repost)
by doodad-js Admin 12 Feb '16

12 Feb '16

(sorry for the repost, but someone told me that I should include "filesystem" in the subject) Hi, I have read the specs (http://www.boost.org/doc/libs/1_60_0/libs/filesystem/doc/reference.html#tem p_directory_path) and found the following issues with Android devices: - It should first try to get the application's cache directory from the API level 1 "getCacheDir" so that temporary files created by the application can be easily and automatically removed. - The function fails back to the hard coded value "/data/local/tmp". But I think it should use the environment variable "ANDROID_DATA" when available and append "/local/tmp" to it. - The "/data/local/tmp" folder is denied access on my Android device. I don't have any other suggestion than the application's cache folder like I first mentioned. I'm not a core developer and the information provided on this email maybe erroneous or incomplete. My apologies if I'm entirely wrong. Thanks, Claude Petit

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Contribution to Boost as Developer
by aman kumar singh 11 Feb '16

11 Feb '16

Developers, I am Aman Kumar Singh,Senior Year,NIT Mizoram,India(Computer Science and Engineering).I am new to open source development. I like coding especially in C++.I have 6 years of working experience in C++.I am very much interested in contributing to open source development especially in Boost.I want to apply for Google Summer of Code 2016 in future.Can somebody help me out.I am ready to dedicate my full time to it once I get aware of the system fixing bugs and further contributing to big projects. I am left with very less time for GSoC and this time I want to be part of it.Please help me out. Thanking you, Aman Kumar Singh, NIT Mizoram, India

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problem with ASIO
by Juan Dent 10 Feb '16

10 Feb '16

Thank you so much Bjorn Reese!! you solved my problem with ASIO. My instincts were correct in that the stream was destroying the std::cout. ::dup() solves this. Best regards, Juan

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Re: [boost] Problem with ASIO
by Bjorn Reese 10 Feb '16

10 Feb '16

On 02/10/2016 02:27 AM, Juan Dent wrote: > posix::stream_descriptor stream{ioservice, STDOUT_FILENO}; Here you take over ownership of stdout, so it will be closed by the stream destructor. A quick fix is to pass a copy of the file descriptor with ::dup(STDOUT_FILENO) as shown in the posix_chat_client.cpp example.

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temp_directory_path and Android devices
by doodad-js Admin 10 Feb '16

10 Feb '16

Hi, I have read the specs (http://www.boost.org/doc/libs/1_60_0/libs/filesystem/doc/reference.html#tem p_directory_path) and found the following issues with Android devices: - It should first try to get the application's cache directory from the API level 1 "getCacheDir" so that temporary files created by the application can be easily and automatically removed. - The function fails back to the hard coded value "/data/local/tmp". But I think it should use the environment variable "ANDROID_DATA" when available and append "/local/tmp" to it. - The "/data/local/tmp" folder is denied access on my Android device. I don't have any other suggestion than the application's cache folder like I first mentioned. I'm not a core developer and the information provided on this email maybe erroneous or incomplete. My apologies if I'm entirely wrong. Thanks, Claude Petit

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