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

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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Re: [boost] Boost CRC maintainer (Daryle Walker) missing in action?
by Olaf van der Spek 19 Jun '17

19 Jun '17

Hi Daryle, Any luck on your new setup? Gr, Olaf On Mon, Nov 28, 2011 at 1:11 AM, Daryle Walker <darylew(a)gmail.com> wrote: > I can look at it once I've finished my new setup. > > I had to reset my computer after a partial crash years ago. I never > got around to recreating my programming setup. My computer had been > at its maximum Operating System level back then, which is now 3 > versions behind. For the past few months, I've had my sister's old > laptop, with Windows Vista, and am trying to add a programming setup > to it now. > > > On Tue, Nov 22, 2011 at 7:18 AM, Beman Dawes <bdawes(a)acm.org> wrote: >> Hi Daryle, >> >> This guy has volunteered to take over maintenance of Boost CRC. Should >> we take him up on his offer? > >> ---------- Forwarded message ---------- >> From: >> Date: Wed, Nov 2, 2011 at 7:51 AM >> Subject: [boost] Boost CRC maintainer (Daryle Walker) missing in action? >> To: boost(a)lists.boost.org >> >> >> Hi, >> >> It looks like the Boost CRC maintainer (Daryle Walker) is missing in action? >> >> No response to tickets from the past 3 years. What's the procedure in this case? >> >> https://svn.boost.org/trac/boost/ticket/2492 >> https://svn.boost.org/trac/boost/query?component=crc&col=id&col=summary&col… > > -- > Daryle Walker > Mac, Internet, and Video Game Junkie > darylew AT gmail DOT com -- Olaf

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[container] moving a pre-built vector into a flat_set
by Sam Kellett 12 Mar '17

12 Mar '17

a common problem i encounter is that i have two stage's w/r/t to a large collection of data: building and querying. vector is obviously the king of building. flat_set is the king of querying. so what i often tend to do is build up a very large vector, sort it then create a flat_set using the flat_set(ordered_unique_t) constructor. however this still copies the entire vector into the flat_set, right? what i would like to be able to do is move the vector straight into the flat_set, something like: std::vector<T> data; flat_set data_set1(std::move(data)) // move vector in and sort it // or: std::sort(data.begin(), data.end()); // sort vector flat_set data_set2(ordered_unique_t, std::move(data)) // and move it in is this doable (am i just being blind?) or is there plans/interest for this?

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[nowide] Library Updates
by Artyom Beilis 04 Mar '17

04 Mar '17

Hello, Disclaimer: --------------- I recently discovered that virtually all e-mails sent from Yahoo account to any mailing lists go to user's spam due to recent Yahoo's DMARC policy. So I'm sending some important stuff from GMail account that almost certainly was missed: What is Boost.Nowide: -------------------------------- Boost.Nowide is a library that make cross platform Unicode aware programming easier. The library provides an implementation of standard C and C++ library functions, such that their inputs are UTF-8 aware on Windows without requiring to use Wide API. It was inspiration and inspired by http://utf8everywhere.org/ development ideas and policy. Some updates regarding Boost.Nowide ------------------------------- 1. Library moved to github and its format is converted to modular boost layout: https://github.com/artyom-beilis/nowide 2. Fixed unsupported std::ios::ate flag by boost::nowide::fstream 3. Added some C++11 interfaces to boost::nowide::fstream 4. Added integration functionality with boost::filesystem: https://github.com/artyom-beilis/nowide/blob/master/include/boost/nowide/in… Note: that the links to the source code on review schedule aren't relevant, it should be: - Code: https://github.com/artyom-beilis/nowide - Documentation: http://cppcms.com/files/nowide/html/ Also the library is still looking for review manager. Artyom Beilis P.S.: I'm sorry if you are getting this as "duplicate"

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bad include guards
by Steven Watanabe 26 Jan '17

26 Jan '17

AMDG The following pairs of files have identical include guards ./boost/concept_check/general.hpp ./boost/concept/detail/msvc.hpp ./boost/concept_check/msvc.hpp ./boost/concept/detail/msvc.hpp ./boost/filesystem/cerrno.hpp ./boost/cerrno.hpp ./boost/interprocess/containers/tree.hpp ./boost/interprocess/containers/detail/tree.hpp ./boost/mpl/min_max.hpp ./boost/mpl/max.hpp ./boost/mpl/vector/aux_/front.hpp ./boost/mpl/list/aux_/front.hpp ./boost/multi_index/identity_fwd.hpp ./boost/multi_index/identity.hpp ./boost/python/pointee.hpp ./boost/python/detail/pointee.hpp ./boost/spirit/phoenix/closures.hpp ./boost/lambda/closures.hpp ./boost/xpressive/proto/v1_/proto_typeof.hpp ./boost/xpressive/proto/proto_typeof.hpp ./libs/config/test/boost_no_dep_nested_class.ipp ./libs/config/test/boost_has_vc6_mem_templ.ipp ./libs/config/test/boost_no_mem_templates.ipp ./libs/config/test/boost_has_vc6_mem_templ.ipp ./libs/config/test/boost_no_std_allocator.ipp ./libs/config/test/boost_has_vc6_mem_templ.ipp ./libs/conversion/test.hpp ./libs/any/test.hpp ./libs/interprocess/example/print_container.hpp ./libs/interprocess/example/printcontainer.hpp ./libs/interprocess/test/expand_bwd_test_template.hpp ./libs/interprocess/test/allocation_test_template.hpp ./libs/interprocess/test/printcontainer.hpp ./libs/interprocess/example/printcontainer.hpp ./libs/interprocess/test/print_container.hpp ./libs/interprocess/example/printcontainer.hpp ./libs/iostreams/test/detail/utf8_codecvt_facet.hpp ./boost/detail/utf8_codecvt_facet.hpp ./libs/regex/test/regress/test_regex_search.hpp ./libs/regex/test/regress/test_partial_match.hpp ./libs/serialization/test/C.hpp ./libs/serialization/test/A.hpp ./libs/xpressive/perf/regex_comparison.hpp ./libs/regex/performance/regex_comparison.hpp ./tools/inspect/time_string.hpp ./tools/common/time_string.hpp In Christ, Steven Watanabe

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[config] RFC PR 82
by Domagoj Saric 01 Aug '16

01 Aug '16

Hi everyone, I am finally getting back to (trying to) contributing some of my personal projects to Boost. For two of those, Err (https://github.com/psiha/err) and especially Functonoid (a C++11 generalization and rewrite of my previous Boost.Function related work) I need some lower level codegen and/or optimiser control functionality (i.e. portable macros wrapping toolset specific attributes and pragmas) that I've added to my personal fork of Boost.Config and which I've now submitted in the subject PR (https://github.com/boostorg/config/pull/82) I don't expect this PR to be accepted as is/'just like that' so I'm opening this thread where we can discuss which of those changes/macros are welcome, which need more work and which, for some reason, should not be part of Boost.Config (and which, in turn then, I have to move to some 'internal implementation headers' in libraries that will need them). To avoid 'spamming' (and save time;) I'll skip the explanation of the individual macros as I expect them to mostly be self-explanatory (if not from their name then from the minimal Boost.Config documentation additions that are part of th PR). ps. I'll be on the (off) road for the next three weeks so I don't know when I'll be able to respond until I get back... -- "What Huxley teaches is that in the age of advanced technology, spiritual devastation is more likely to come from an enemy with a smiling face than from one whose countenance exudes suspicion and hate." Neil Postman

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[Fit] pipable order of the arguments
by Vicente J. Botet Escriba 05 Mar '16

05 Mar '16

Hi, I would like to know what other think about the order of the pipe (See this issue https://github.com/pfultz2/Fit/issues/5) What would be the expected meaning of auto r1 =1 | pipable(f)(2); f(1,2) or f(2,1)? What would be the expected meaning of auto f2 = partial(f)(2); auto r1 =1 | pipable(f2); f(1,2) or f(2,1)? As the operator| has left-to-right associativity, we can not do auto x = 1 | 2 | pipable(f); We would need a way to pack the parameters auto x = forward_as_tuple(1, 2) | pipable(f); but this wouldn't compile as f has two parameters. or use parenthesis auto x = 1 | (2 | pipable(f)); and the result will be f(2, 1). Any ideas? Best, Vicente Vicente

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[MSM] Is there any interest in C++14 Boost.MSM-eUML like library which compiles up to 60x quicker whilst being a slightly faster too?
by Krzysztof Jusiak 18 Feb '16

18 Feb '16

Dear Boosters, I have recently released 1.0.0 version of experimental C++14 Boost.MSM-lite. Your scalable C++14 header only eUML-like meta state machine library with no dependencies, which outperform Boost.MSM - eUML in: - faster compilation times - up to 60x times faster! - smaller executable size - up to 15x smaller - slightly better performance - smaller memory usage - short error messages Check it out yourself online! http://boost-experimental.github.io/msm-lite/examples/index.html#hello-world Performance Results: http://boost-experimental.github.io/msm-lite/overview/index.html#performance Source code: https://github.com/boost-experimental/msm-lite Documentation: http://boost-experimental.github.io/msm-lite Any feedback is more than welcome! Cheers, Kris

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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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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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[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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[smart_ptr] Interest in the missing smart pointer (that can target the stack)
by Noah 09 Feb '16

09 Feb '16

Hi all, I'm new here. Here goes: I propose a new smart pointer called, say "registered_ptr", that behaves just like a native C++ pointer, except that its value is (automatically) set to null_ptr when the target object is destroyed. This kind of smart pointer already exists and is being used in the form of, for example, QPointer and Chromium's WeakPtr (http://doc.qt.io/qt-5/qpointer.html and https://code.google.com/p/chromium/codesearch/#chromium/src/base/memory/wea…) although those implementations only apply to a specific set of object types. There's also std::experimental::observer_ptr (http://en.cppreference.com/w/cpp/experimental/observer_ptr) which seems to be trying to serve a similar purpose, but with none of the functionality. This might be as far as you need to read to decide if you think it's a good idea or not. The rest of this (kind of long) post addresses some of the details and motivation. It's instructive to compare this "registered_ptr" with (std::)shared_ptr. Both have a (modest) performance cost, although registered_ptr's performance cost is significantly lower, as will be discussed later. Both can have a significant "code safety" benefit when used for that purpose - i.e. reduce or eliminate the possibility of invalid access of an object that has already been destroyed. And both have a functional purpose other than safety or convenience (or just being a regular pointer). That functional purpose is to deal with situations when it is not easy to predict in advance (i.e. at compile time) when an object will be referenced (and stop being referenced). shared_ptr deals with these type of situations by ensuring that the object remains "alive" for as long as there are any (owning) references to the object. This assumes that the object has no "curfew". But one can imagine situations where an object needs to be destroyed at or by a certain time or event. If the object is exclusively holding an in demand resource, or security lock for example. In these cases one might prefer that late attempted references to the object fail (safely) rather than have the object's destruction delayed. registered_ptrs might be more suitable for these situations. So from this comparison it's hard to argue for the inclusion of shared_ptr and the omission of registered_ptr in the library. registered_ptr can be thought of as a kind of "non-intrusive" counterpart to shared_ptr. "But wait", you say, "shared_ptr already has a non-intrusive counterpart. Namely weak_ptr." Yes, but the difference between weak_ptr and registered_ptr is that registered_ptr is independent, not just an appendage of shared_ptr. And registered_ptr can point to stack allocated objects (just like native C++ pointers can), but at the cost of "thread safety". Referencing an object on another (asynchronous) thread's stack is inherently not safe, right? Some may be concerned with this lack of thread safety - I am not, I don't think we should be encouraging casual asynchronous object sharing - but the performance dividend of getting to put the target object on the stack rather than the heap more than makes up for it in my opinion. So I've actually already had cause to implement, and use, a version of this "registered_ptr" (I actually called it "TRegisteredPointer"), and in practice it works great. But there are, arguably, a couple of issues. Besides the thread safety (non-)issue, my implementation can only target types that can act as base classes. By default most classes can act as a base class, but native types like int, bool, etc. cannot. In my case, this is not a big issue because TRegisteredPointer is actually part of a small library that includes (safer) substitutes for int, bool and size_t that can act as base classes. The good thing is that it does seem to serve its purpose of not only being safe, but also faster than shared_ptr. Much faster when targeting stack objects as one would expect, but also faster when targeting heap objects according to my simple benchmarks (msvc2013 - Windows 7 - Haswell). My implementation can be found here: https://github.com/duneroadrunner/SaferCPlusPlus. It's in the file called "mseregistered.h". Examples of it in action can be found in the file called "msetl_example.cpp", near the end. No decent documentation yet, but the examples are commented and it should be clear what's going on. So far I've posited that the argument for registered_ptr is at least as good as the argument for shared_ptr. But let me make a further argument for why I think it's particularly important to include registered_ptr. First, let me make an argument for "safe" pointers in general. By safe pointers, I mean pointers that have zero chance of participating in a dereference to invalid memory. This will usually imply that the safe pointer will do a runtime check and throw an exception if an invalid dereference is attempted. Now, I subscribe to the C++ "trust the programmer" philosophy, so I agree that programers should have the option of avoiding these runtime checks. But security (and by extension, language safety) is so important these days that programmers should also have the option of having these runtime checks when desired. So I'm suggesting that all the smart pointers (shared_ptr, unique_ptr, etc.) come in "safe" versions as well. There is already some precedent for safe and unsafe options. For example, std::vector<> provides both the "unsafe" [] operator and the "safe" at() function. And ultimately it needs to be properly measured, but I would think that the performance cost of this kind of runtime check should be quite modest. There is plenty of opportunity for optimizing compilers to strip them out when not needed and of course these sorts of runtime checks are a favorite food of branch predictors in modern cpus right? I haven't put a lot of effort into this, but my simple benchmarks show checked dereferences being only modestly slower than unchecked dereferences. (The "msetl_example.cpp" file includes some simple benchmarks.) So why does this make registered_ptr so important? Because the "safe" version of registered_ptr would be the safe pointer with the lowest performance cost. Perhaps low enough for the safety benefits to be widely considered worth the cost. Of course the ideal would be smart pointers that could distinguish between stack allocated objects and heap allocated objects. Unfortunately, as far as I know, (standard) C++ doesn't seem to give us that facility. If we can't have those, I think we need a smart pointer that can at least accommodate stack allocated objects. Right? Noah

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expected/result/etc
by Michael Marcin 07 Feb '16

07 Feb '16

Some months ago there was a lot of discussion regarding Rust style return values for non-exceptional error handling. Did anything ever come of this? Is there a useable library? Apologies if I missed an announcement (I've been away for a bit).

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Is there interest in Computable Calculus?
by Alexander Lauser 05 Feb '16

05 Feb '16

Hi, An arithmetic operation produces a new function using the functions in the operands and some simple expression manipulations. if I gather it right, then what you propose is basically a Computer Algebra System (i.e., a system for manipulating reals by symbolic expressions). What specifically would the goal of the library be? Best, Alex

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updated version of safe integer library
by Robert Ramey 05 Feb '16

05 Feb '16

I've updated my safe integer library. Pointers to the most recent documentation and code can be found at www.blincubator.com . Or one can use documentation http://htmlpreview.github.io/?https://github.com/robertramey/safe_numerics/… repository: https://github.com/robertramey/safe_numerics I've resolved added more tests. added more examples and explanation of them added facilities to enforce a guarantee of zero runtime penalty added new section to the documentation of the above added more documentation regarding the library implementation. and other stuff. There is still a little more to do. But there is nothing that I know about that would prevent users from using this library right now to implement guaranteed correct integer arithmetic in their applications. Of course I'm interested any feedback and/or observations anyone want's to offer. Robert Ramey

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Transferring the boost-qvm github repository to Boost
by Emil Dotchevski 03 Feb '16

03 Feb '16

Hello, Ron Garcia, one of the Boost Review Wizards, has directed me to ask the mailing list about the exact procedure for transferring the boost-qvm github repo to Boost. I believe I need to have some kind of permissions to be able to use the built-in github repo transferring mechanism. Thanks, Emil

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Adding Metaparse to the master branch
by Abel Sinkovics 31 Jan '16

31 Jan '16

Hi, I've created a pull request to add the Metaparse tests to the Boost regression tests (#113) on the develop branch (Metaparse itself is already part of the develop branch, only the regression test integration is missing). I would like Metaparse to be added to the master branch as well. I have created pull request #112 for that. Please let me know what else is needed. Thanks, Abel

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[tools/GSoC] static code analysis?
by Oliver Kowalke 30 Jan '16

30 Jan '16

Hi, would it be possible to provide a boost-tool or maybe a boost-GSoc project that enables static code analysis for boost developers? clang-tidy ( http://clang.llvm.org/extra/clang-tidy/) could be used for this purpose. Oliver

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Re: [boost] [coroutine] x86 msvc11 stack corruption
by AVZ 29 Jan '16

29 Jan '16

Just want to share workaround which work for our company. (Fiber fix was not acceptable for that application) Debugging differences in make_fcontext between 1.53 vs 1.57, I found that in 1.53 context area is cleanned with 0, but not in 1.57. So we added explicit clear after line 100 in make_x86_64_ms_pe_masm.asm: sub rax, 0128h * ; memset context area pxor xmm0, xmm0 movaps [rax+008h], xmm0 movaps [rax+018h], xmm0 movaps [rax+028h], xmm0 movaps [rax+038h], xmm0 movaps [rax+048h], xmm0 movaps [rax+058h], xmm0 movaps [rax+068h], xmm0 movaps [rax+078h], xmm0 movaps [rax+088h], xmm0 movaps [rax+098h], xmm0 movaps [rax+0a8h], xmm0 movaps [rax+0b8h], xmm0 movaps [rax+0c8h], xmm0 movaps [rax+0d8h], xmm0 movaps [rax+0e8h], xmm0 movaps [rax+0f8h], xmm0 movaps [rax+108h], xmm0 movaps [rax+118h], xmm0 * ; third arg of make_fcontext() == address of context-function mov [rax+0118h], r8 With that we are getting same behavior as 1.53 - no crash on DLL load. Thanks, AZ -- View this message in context: http://boost.2283326.n4.nabble.com/coroutine-x86-msvc11-stack-corruption-tp… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[Iterator] [PR] Fix for documentation #8010
by Nathan Wilson 29 Jan '16

29 Jan '16

Hi, As a followup to my inquiry about maintaining the Iterator Library about a month back, I wanted to create PR for a simple documentation fix. So, here it is: https://github.com/boostorg/iterator/pull/21 Please let me know if there are any thoughts and/or if I'm doing something incorrectly. Thanks! Nate

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Interest in some Algorithms
by Dean Michael Berris 29 Jan '16

29 Jan '16

Hi Boost! It’s been a while, I hope you all have been doing well. I wanted to ask whether anybody’s interested in a couple of algorithms, to be made part of the Boost.Algorithm library. One is tentatively named ‘set_inplace_difference' which has the following synopsis: template <class I1, class I2> I1 set_inplace_difference(I1 f1, I1 f2, I2 f2, I2 l2); template <class I1, class I2, class C> I1 set_inplace_difference(I1 f1, I1 f2, I2 f2, I2 l2, C comp); It’s essentially a set_difference which re-uses the storage of the range [f1, l1). It takes elements from [f1, l1) that are in [f2, l2) and moves them to [p, l1) where p is the partition point (or the new “end”). This is best used in conjunction with “erase” on vectors and/or std::deque. These algorithms return p. Another is tentatively named ‘set_inplace_intersection’ which instead of the above which does the difference, does an intersection instead. Requirements on I1 and I2 are that they are RandomAccess iterators, and that they are sorted. I haven’t figured out whether partially-sorted is a sufficient condition. I also haven’t figured out whether it would work for weaker iterator classes, but so far my implementation relies on std::lower_bound and std::upper_bound. If there’s enough interest, I can prepare a pull request after going through my employer’s open-source patching process. Looking forward to hearing your thoughts! Cheers

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C++Now 2016 Registration is Open
by Jon Kalb 28 Jan '16

28 Jan '16

Boost Developers, Registration is now open for this year¹s C++Now (put on by Boost). http://cppnow.org/2016-conference/announcements/2016/01/28/registration-is-o pen.html The conference has sold out the last three years and is expect to do say again this year. Do not put off registering. Note that session submitters should not register until they receive instructions from Marshall Clow, our conference registrar. See you in Aspen! Jon

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Interest in library for nested containers?
by Alberto Marnetto 28 Jan '16

28 Jan '16

Hello, is there interest in adding a library for nested containers (including a flattening view, a function counting the scalar elements etc.) to Boost? A working version is available at https://github.com/AlbertoMarnetto/multidim . If the concept and the interface are suitable for a submission – in particular if the requirement of a C++11 compiler is acceptable and the small number of functionalities is not a problem – I can proceed to restructure the library to meet Boost's style guidelines. Regards, Alberto Marnetto

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QuickBook generate table of references?
by Nat Goodspeed 27 Jan '16

27 Jan '16

I have a biggish document consisting of a number of different .qbk files -- big enough to make it unreasonable to start over with a different toolchain. I would like to mark up particular methods of particular classes in such a way that QuickBook will produce a consolidated list of links to those methods. I read a little about DocBook being able to generate tables of figures, etc., but between QuickBook syntax and the final output document, my mental model has a big "then a miracle occurs" cloud. Will someone please show me how this is achieved? Thank you!

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Query regarding time complexity requirements of iterators in custom container
by Soul Studios 26 Jan '16

26 Jan '16

Hi there- currently working on Colony, last version I'm working on has achieved constant-time(amortised) time-complexity for iterator operations, except for the random-access operators (+, -, +=, -=, [], >, <, >=, <=). It's not possible to make these constant-time due to the nature of the algorithms and structure of container. Ion pointed out to me that there is an obscure C++ requirement for iterators that all operations be constant-time. Given this, is it worth keeping these in Colony before submitting to Boost, or would it be best to remove them and make the iterator bidirectional-only prior? Cheers, Matt

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[serialization] Custom archive and arrays
by Bjorn Reese 23 Jan '16

23 Jan '16

I am currently adding support of C++ arrays to a custom oarchive. My archive inherits from boost::archive::detail::common_oarchive and implements save_override(), which will pass any unknown type to boost::archive::save(). This enables me to implement non-intrusive serialization. When I pass an array to boost::archive::save(), it detects that this is an array and then calls detail::save_array_type. This is where my problem starts, as the function is hardcoded to always store a prefixed array count, which is illegal in the format that my custom archive uses. Would it be possible to lift this restriction? My current workaround is to add an overload for arrays to my custom archive, i.e. template <typename T, std::size_t N> void save_override(const T (&data)[N]);

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[type_traits] Tests for implicit convertibility?
by John Maddock 22 Jan '16

22 Jan '16

Folks, I suspect we may have unintentionally backed ourselves into a corner with is_convertible/is_constructible. While trying to fix https://svn.boost.org/trac/boost/ticket/11922 I found I needed to SFINAE-out some conversion operators when the conversion already exists (as an implicit constructor in the target type). So far so easy, but consider: class Int { public: Int(const int& i) {}; Int(const Int& i) = delete; }; static_assert(is_convertible<int, Int>::value, "Ooops"); Now you would think this would pass right? But it doesn't (at least on GCC and clang), and this is true for both boost:: and std:: type_traits and appears to be an unintended side effect of the way is_convertible is defined, that a valid copy constructor is required on the target type. Of course: is_constructible<Int, int>::value is true, but that also catches explicit constructors. So... have we backed ourselves into a corner or do we still have a way to test for implicit-constructibilty that doesn't also require copy-constructibility on the target type? Thanks, John.

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test matrix messages
by Robert Ramey 22 Jan '16

22 Jan '16

I have a certain number of failures for the tests of the serialization library on the test matrix. If I go to get the messages associated with the failure, I rarely get any helpful information. Here are a couple of common cases: http://www.boost.org/development/tests/develop/developer/output/teeks99-08c… http://www.boost.org/development/tests/develop/developer/output/igaztanaga-… Can anything be done about this? Robert Ramey

1 0

[gsoc16] Attn: We need 2016 mentors and project ideas for Boost!
by Niall Douglas 21 Jan '16

21 Jan '16

Dear Boost community, We are now within one month of the beginning of Google Summer of Code 2016! Last year's GSoC was a particularly momentus one as we witnessed the approval by the community for Boost.Hana to enter Boost - congratulations to Louis and his mentor Joel for bringing to Boost a very exciting new C++ library which pushes C++ compilers to their limits. We have also seen greatly improved retention of GSoC students in the community thanks to the improved student selection procedures introduced last year, and the fresh blood brought into Boost has been very evident on the mailing list this year. As part of filling in our application for 2016, we must supply to Google a list of potential GSoC mentors and potential GSoC projects for summer 2016 in order to be approved as an organisation this year. Therefore a lengthy page of awesome project ideas at https://svn.boost.org/trac/boost/wiki/SoC2016 before *February 8th* would be an enormous help to getting us approved again this year and bringing to Boost another US$35,000 of Google funding. If you think yourself able to mentor a student doing some work on Boost this summer, *please* consider adding a description of the proposed work item and your name to the list. Last year we had more slots awarded to us by Google than we had good combinations of student and mentor, so we had to return slots which I believe has not happened here at Boost GSoC in at least a decade. That means that your project ideas have a better chance than ever of receiving funding if you can find a good student, and that is best done by getting project ideas floated *early*. If you want to know more about mentoring a Google Summer of Code funded student work before you nominate yourself, please feel free to ask on the main Boost developers mailing list boost(a)lists.boost.org or via gsoc-admin(a)boost.org. Thank you in advance for your time. --- Boost C++ Libraries Google Summer of Code 2016 admin https://svn.boost.org/trac/boost/wiki/SoC2016

3 2

please add safe numerics to the review queue
by Robert Ramey 21 Jan '16

21 Jan '16

Any chance I could get safe numerics added to the Boost Review queue? THe link to the incubator is here: http://rrsd.com/blincubator.com/bi_library/safe-numerics/?gform_post_id=426 documention here: http://htmlpreview.github.io/?https://github.com/robertramey/safe_numerics/… and github repo here: https://github.com/robertramey/safe_numerics Robert Ramey

1 0

[gsoc16] Can I quickly check if the below really is the best approach?
by Niall Douglas 19 Jan '16

19 Jan '16

Dear Boost, In the prototype https://svn.boost.org/trac/boost/wiki/SoC2016 at https://goo.gl/1CQAuQ I claim "Even with all of Boost's facilities [1] and using C++ 14, this program represents the currently best available method of implementing a static constant associative map of keys to values" and you can find either the code at the link or pasted below. Can I quickly check here if that claim is true? Is there a better way than my example program? BTW by static constant associative map of keys to values I mean the thing me and Tony van Eerd were speaking about here last year and the year before, and indeed frequently at BlackBerry! Niall [1]: I believe Boost.Hana could implement a static constan associative map quite easily, but I'd be fairly sure Hana will likely be beyond most students. --- cut --- #include <initializer_list> #include <experimental/string_view> #include <map> #include <unordered_map> #include <iostream> using std::experimental::string_view; enum class weekday { sunday, monday, tuesday, wednesday, thursday, friday, saturday }; // initializer_list, pair and string_view are constexpr, so this list can be constexpr // (i.e. lives in the mind of the compiler only and has zero representation in generated code) #define STRING_VIEW(str) { str, sizeof(str)-1 } constexpr std::initializer_list<std::pair<const string_view, weekday>> string_to_weekday { { STRING_VIEW("sunday"), weekday::sunday }, { STRING_VIEW("monday"), weekday::monday }, { STRING_VIEW("tuesday"), weekday::tuesday }, { STRING_VIEW("wednesday"), weekday::wednesday }, { STRING_VIEW("thursday"), weekday::thursday }, { STRING_VIEW("friday"), weekday::friday }, { STRING_VIEW("saturday"), weekday::saturday } }; int main(void) { { // Calls malloc() at least 7 times static const std::map<string_view, weekday> to_weekday1 = string_to_weekday; std::cout << "'monday' maps to " << static_cast<int>(to_weekday1.at("monday")) << std::endl; std::cout << "'friday' maps to " << static_cast<int>(to_weekday1.at("friday")) << std::endl; // Calls free() at least 7 times } { // Calls malloc() at least 8 times static const std::unordered_map<string_view, weekday> to_weekday2 = string_to_weekday; std::cout << "'monday' maps to " << static_cast<int>(to_weekday2.at("monday")) << std::endl; std::cout << "'friday' maps to " << static_cast<int>(to_weekday2.at("friday")) << std::endl; // Calls free() at least 8 times } return 0; } -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

13 28

whatever happened to the constrained value library?
by Robert Ramey 18 Jan '16

18 Jan '16

I just stumbled upon the following announcement. http://lists.boost.org/boost-announce/2010/09/0265.php But I don't see any such library as part of boost. What's up with this? Robert Ramey

3 3

Re: [boost] [interprocess] boost::hash - different values for the same input?
by Daniel James 17 Jan '16

17 Jan '16

I altered the subject to include interprocess, since this is relevant there. On 9 December 2015 at 20:13, trafdev <trafdev(a)mail.ru> wrote: > > As per hash_range docs > (http://www.boost.org/doc/libs/1_59_0/doc/html/hash/reference.html#boost.has…) > > "This hash function is not intended for general use, and isn't guaranteed to > be equal during separate runs of a program - so please don't use it for any > persistent storage or communication." > > As per code > (http://www.boost.org/doc/libs/1_59_0/boost/functional/hash/hash.hpp) it > uses hash_combine_impl which doesn't use any random, process_id etc values > which might change during new process launches. > > At the same time, in an example describing container usage in the shared > memory > (http://www.boost.org/doc/libs/1_59_0/doc/html/interprocess/allocators_conta…) > boost::hash is being used: > > typedef boost::unordered_map > < KeyType , MappedType > , boost::hash<KeyType> ,std::equal_to<KeyType> > , ShmemAllocator> > MyHashMap; > > My question is: is it safe to use boost::hash in a shared (persistent) > storage or it's safe only for a particular (non-pointer) types? > > In this case, boost::hash docs should be changed to mention this exceptions, > because otherwise no one could use boost::hash in a shared memory > containers. Sorry about the very slow reply. I'm afraid the answer is that it depends. The reason why I originally wrote that note was because it can generate different hash values when compiled for different platforms or architectures, e.g. a 32-bit executable might generate a different hash value to a 64-bit executable. Also, I occasionally change the algorithm in new versions of boost (and probably will in the next version). For interprocess this currently won't be an issue if all the processes are using the same executable, or using executables built with same version of boost and the same architecture, but could be a problem if that isn't the case. So maybe the Interprocess documentation needs to explain this. But there's another problem coming up. The last proposal I saw for a standard generic hash function will support randomized hash functions (such as siphash) which will only work with interprocess if they are somehow seeded identically. I'll want to support whatever is accepted to the standard (although maybe as a separate library). I'll need to catch up with how that is progressing, as I haven't kept up to date.

5 13

Any-Range containing transformed range fails when compiled with optimizations
by Auer, Jens 17 Jan '16

17 Jan '16

Hi, I have a program which produces different results based on the compiler options. The program uses a boost::any_range containing a transformed range where the transformation function just returns a new object of a simple struct: #include <vector> #include <boost/range.hpp> #include <boost/range/any_range.hpp> #include <boost/range/adaptor/transformed.hpp> #include <iostream> template<typename T1, typename T2> void ASSERT_EQ(T1 x,T2 y) {assert(x == y);}; struct SourceEvent { std::uint32_t event; void* ptr; }; int main() { using boost::adaptors::transformed; using R = boost::any_range<SourceEvent, boost::forward_traversal_tag, SourceEvent, std::ptrdiff_t>; std::vector<std::int32_t> v(100); R r = v | transformed( [](auto const&) {return SourceEvent{0u, nullptr};} ); auto t = v | transformed( [](auto const&) {return SourceEvent{0u, nullptr};} ); ASSERT_EQ( 100u, boost::size(r) ); ASSERT_EQ( 100u, boost::size(t) ); for (auto const& i: t) { ASSERT_EQ(0u, i.event ); ASSERT_EQ(nullptr, i.ptr); } for (auto const& i: r) { ASSERT_EQ(0u, i.event ); ASSERT_EQ(nullptr, i.ptr); } std::cout << "OK" << std::endl; return 0; } When compiled without optimization, it just prints ok. The same source compiled with optimizations asserts, and prints some interesting warnings: In file included from /usr/local/boost-1.60.0/include/boost/range/detail/any_iterator.hpp:22:0, from /usr/local/boost-1.60.0/include/boost/range/any_range.hpp:17, from prog.cc:3: /usr/local/boost-1.60.0/include/boost/range/detail/any_iterator_wrapper.hpp: In member function 'boost::range_detail::any_forward_iterator_wrapper<WrappedIterator, Reference, Buffer>::reference boost::range_detail::any_forward_iterator_wrapper<WrappedIterator, Reference, Buffer>::dereference() const [with WrappedIterator = boost::iterators::transform_iterator<boost::range_detail::default_constructible_unary_fn_wrapper<main()::<lambda(const auto:1&)>, SourceEvent>, __gnu_cxx::__normal_iterator<int*, std::vector<int> >, boost::iterators::use_default, boost::iterators::use_default>; Reference = SourceEvent; Buffer = boost::any_iterator_buffer<64ul>; boost::range_detail::any_forward_iterator_wrapper<WrappedIterator, Reference, Buffer>::reference = SourceEvent&]': /usr/local/boost-1.60.0/include/boost/range/detail/any_iterator_wrapper.hpp:302:57: warning: function may return address of local variable [-Wreturn-local-addr] return dereference_cast<reference>(*m_it); ^ /usr/local/boost-1.60.0/include/boost/range/detail/any_iterator_wrapper.hpp:302:52: note: declared here return dereference_cast<reference>(*m_it); ^ prog.exe: prog.cc:7: void ASSERT_EQ(T1, T2) [with T1 = unsigned int; T2 = unsigned int]: Assertion `x == y' failed. Aborted The example is compiled with gcc 5.2 and boost 1.60 (http://melpon.org/wandbox/permlink/QF1qyw5bWHKwyKJ8) Is there an error in my code? I would guess that transforming a range into a range of new objects of another type is quite common, so it should work. I am also curious why the warning is only emitted when compiling with optimizations. Best wishes, Jens -- Jens Auer | CGI | Software-Engineer CGI (Germany) GmbH & Co. KG Rheinstraße 95 | 64295 Darmstadt | Germany T: +49 6151 36860 154 jens.auer(a)cgi.com<mailto:jens.auer@cgi.com> Unsere Pflichtangaben gemäß § 35a GmbHG / §§ 161, 125a HGB finden Sie unter de.cgi.com/pflichtangaben<http://de.cgi.com/pflichtangaben>. CONFIDENTIALITY NOTICE: Proprietary/Confidential information belonging to CGI Group Inc. and its affiliates may be contained in this message. If you are not a recipient indicated or intended in this message (or responsible for delivery of this message to such person), or you think for any reason that this message may have been addressed to you in error, you may not use or copy or deliver this message to anyone else. In such case, you should destroy this message and are asked to notify the sender by reply e-mail.

3 7

Re: [boost] [gsoc16] Can I quickly check if the below really is the best approach?
by Shangtong Zhang 16 Jan '16

16 Jan '16

Hi, > // At global scope, allocates no memory whatsoever > static const constexpr static_map<int, const char *> map { > { 5, "apple" }, > { 8, "pear" }, > { 0, "banana" }, > ... > }; > // Works, constexpr "apple" > constexpr const char *what_is_5 = map[5]; > // Works > assert(map[5] && !strcmp(map[5], "apple"); > // Works > map[5]="orange"; > assert(map[5] && !strcmp(map[5], "orange"); > // Throws exception as there is no key 6 > map[6]; > map.at <http://map.at/>(6); I have difficulty understanding this, As variable map is const and constexpr, how can map[5]=“orange” work? I don’t know how to implement this, where to store the “orange”. Could anyone help me? Thanks, Shangtong Zhang, Senior Student, School of Computer Science, Fudan University, PRC.

2 1

[gsoc16]Interest in static map
by Shangtong Zhang 15 Jan '16

15 Jan '16

Hi Niall Douglas, I’m interested in the project static map and want to contribute to it in gsoc 2016. And I try to start with the programming competency test. Following is what I have done, https://github.com/ShangtongZhang/StaticMap/blob/master/main.cpp <https://github.com/ShangtongZhang/StaticMap/blob/master/main.cpp> Could you please give me some advice? In addition, I’m a little confused with // This should fail elegantly and usefully ... //constexpr std::array<unsigned, 0> string_hashes_fail = hash_strings(5); My understanding is that it will raise a run-time exception, is it right? Thanks, Shangtong Zhang, Senior Student, School of Computer Science, Fudan University, PRC.

2 1

Is there interest in Computable Calculus?
by Damian Vicino 15 Jan '16

15 Jan '16

Hi, I’m interested in developing basic support of “real numbers” for computable calculus applications. In computable calculus, reals have infinite precision (certain restrictions may apply). The usual approach is representing numbers as functions producing digits. An arithmetic operation produces a new function using the functions in the operands and some simple expression manipulations. When a number needs to be evaluated (e.g., for comparisons where expression rules are unknown), enough digits for reaching an answer are generated using the functions. For example, 3.14 < pi requires generating 3 digits to answer “true”. The algorithms for arithmetic operations and evaluation are well known, and multiple implementations were developed (mostly in the 90s). However, I couldn’t find an open source implementation and had to come up with my own for working in a project during the last 2 years. My preferred reference for the required algorithms is the book: Aberth, Oliver. Computable Calculus. Academic Press, 2001. In particular, my initial scope would be the 4 arithmetic operations (+, -, *, /), and the comparison operators (<, =) for reals. Someone is interested in such a library in boost?

4 4

IS THERE A WAY TO FIND IF A CERTAIN TYPE HAS A CERTAIN MEMBER?
by Juan Dent 15 Jan '16

15 Jan '16

> HI, > > > I have read that via enable_if and other constructs, one can declare a member of a type conditionally. > > What I need is a way to be able to test whether a certain type has a certain method or member data, so that I can call it or use it accordingly. > > Does boost have something like this?? > > > Regards, > Juan

4 3

a safe integer library
by Robert Ramey 14 Jan '16

14 Jan '16

Arithmetic operations in C++ are NOT guaranteed to yield a correct mathematical result. This feature is inherited from the early days of C. The behavior of int, unsigned int and others were designed to map closely to the underlying hardware. Computer hardware implements these types as a fixed number of bits. When the result of arithmetic operations exceeds this number of bits, the result will not be arithmetically correct. I have crafted a library to address this issue once and for all. You can find out more about this by checking out the page for Safe Numerics at the boost library incubator. www.blincubator.com I hereby request that this library be added to the boost review queue. I've also made a proposal for the C++ Standards committee to include a simplified version of this library as part of he C++ standard. You can see the proposal at http://www.rrsd.com/software_development/safe_numerics/proposal.pdf Robert Ramey

14 42

ATTENTION: Library requirements..
by Rene Rivera 13 Jan '16

13 Jan '16

Last Summer I brought up the subject of library organization requirements to make it easier to write the development and release tools needed to keep the Boost machine going. See this thread < http://lists.boost.org/Archives/boost/2015/06/223027.php> for a refresher. This morning I committed the first part of the above.. A new set of library requirements that take into account existing practices. Adds some additional integration requirements. And puts in limits to reduce some integration burdens. Please read the new requirements carefully < http://www.boost.org/development/requirements.html#Requirements>. It would be wonderful if authors start making changes as needed immediately. But at some point I, and possible others, will start making changes to all libraries to follow the requirements. So that the release, build, and testing teams can move forward with better support. And of course, more cleanups and such will follow. Hopefully before the next release is out the door. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

16 80

[BPM] Supporting an alternative to meta/libraries.json
by Louis Dionne 13 Jan '16

13 Jan '16

Dear list, Currently, all Boost libraries are required to have a meta/libraries.json file at their root, which contains some meta-data describing the library. As I understand it, this meta-data is then used to generate the list of all libraries with their description when a release is done. I find having such a directory at the root of every library annoying, since it clutters it. Furthermore, for metaprogramming libraries, the name can be slightly confusing since meta/ might be expected to contain something different. I propose that we allow libraries to specify their metadata in a `.boost` file located at their root. Using a dotfile is the most common way of providing information for an external service (for example .travis.yml), and dotfiles are usually more discrete when viewing the project in an editor. Furthermore, making `boost` part of the filename is more descriptive. I have submitted a pull request to BPM [1] adding the ability to fetch the meta data in a .boost file. The meta-data can still be provided in meta/libraries.json, so this should not affect existing libraries. Related questions that we might want to consider: - Should it be .boost.json instead of .boost? - Perhaps we could store the meta-data for all the libraries in the same place, and get rid of the individual meta-data files? - If this suggestion is accepted, is there more to modify than BPM? Regards, Louis [1]: https://github.com/boostorg/bpm/pull/1

5 19

[test] BOOST_TEST macro and std::max
by Benedek Thaler 13 Jan '16

13 Jan '16

Hi, I'd expect the following cheks to pass: BOOST_TEST(3u == (std::max)(0u, 3u)); BOOST_TEST(3u == ((std::max)(0u, 3u))); But both fails with: check 3u == ((std::max)(0u, 3u)) has failed [3 != 7095312] Did I miss something regarding BOOST_TEST usage? Platform: Linux, GCC 5.3, Boost 1.60 Thanks, Benedek

4 15

Re: [boost] asio config.hpp macro redefinition - mistake?
by Curdeius Curdeius 13 Jan '16

13 Jan '16

> > ---------- Wiadomość przekazana dalej ---------- > From: "John M. Dlugosz" <mpbecey7gu(a)snkmail.com> > To: boost(a)lists.boost.org > Cc: > Date: Tue, 12 Jan 2016 17:32:48 -0600 > Subject: [boost] asio config.hpp macro redefinition - mistake? > In file boost_1_59_0\boost\asio\detail\config.hpp line 227 gives a macro > redefinition warning. > (...) > It seems that this is missing a guard or has the if/else things mixed up. > This was fixed some time ago. See https://github.com/boostorg/asio/commit/b9cb61416e1972d7490d91da91df549703f… . Regards, Marek Kurdej

1 0

[fusion]enabler.hpp junk character at start of file
by Aparna Kumta 13 Jan '16

13 Jan '16

All accumulator tests fail when compiled with Oracle Solaris Studio in 'dev' branch as follows: "../boost/fusion/support/detail/enabler.hpp", line 1: Error: A declaration was expected instead of "???". 1 Error(s) and 1 Warning(s) detected. See http://www.boost.org/development/tests/develop/developer/output/oracle-spar… It appears that in file boost/fusion/support/detail/enabler.hpp, there is some junk character at the start of file. This cannot be observed via vi editor, but with ' head -1 enabler.hpp', this can be seen. % head -1 enabler.hpp ��/*===================================== Perhaps these characters should be removed? When I view the file on github, I do not see the issue, however when I try to edit the file, I see it. Will submit a PR. Thanks, Aparna

2 2

[regression] Regression tests for 'develop' has error
by Edward Diener 13 Jan '16

13 Jan '16

Trying to open the regression test results for 'develop' page gives: "Error extracting file: Error code 3 - A severe error in the zipfile format was detected." This has happened numerous times before. Can this be fixed, not only now but permanently ? Surely there must be some way of determining why the zipfile format has a severe error and preventing this in the future.

5 16

asio config.hpp macro redefinition - mistake?
by John M. Dlugosz 13 Jan '16

13 Jan '16

In file boost_1_59_0\boost\asio\detail\config.hpp line 227 gives a macro redefinition warning. // Compliant C++11 compilers put noexcept specifiers on error_category members. #if !defined(BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT) # if (BOOST_VERSION >= 105300) # define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT BOOST_NOEXCEPT # elif defined(__clang__) # if __has_feature(__cxx_noexcept__) # define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT noexcept(true) # endif // __has_feature(__cxx_noexcept__) # elif defined(__GNUC__) # if ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)) || (__GNUC__ > 4) # if defined(__GXX_EXPERIMENTAL_CXX0X__) # define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT noexcept(true) # endif // defined(__GXX_EXPERIMENTAL_CXX0X__) # endif // ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)) || (__GNUC__ > 4) # endif // defined(__GNUC__) # if defined(BOOST_ASIO_MSVC) # if (_MSC_VER >= 1900) # define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT noexcept(true) // ****** here ****** # endif // (_MSC_VER >= 1900) # endif // defined(BOOST_ASIO_MSVC) # if !defined(BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT) # define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT # endif // !defined(BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT) #endif // !defined(BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT) To paraphrase, the block reads # if (BOOST_VERSION >= 105300) // it is: 105900 >= 105300 *# define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT BOOST_NOEXCEPT* ⋮ # if defined(BOOST_ASIO_MSVC) # if (_MSC_VER >= 1900) *# define BOOST_ASIO_ERROR_CATEGORY_NOEXCEPT noexcept(true)* # endif // (_MSC_VER >= 1900) # endif // defined(BOOST_ASIO_MSVC) It seems that this is missing a guard or has the if/else things mixed up.

2 1

[property_tree] Still being maintained?
by Gavin McNiff 12 Jan '16

12 Jan '16

Hi, I was wondering if the Property_Tree library is still being actively maintained. There are 9 GitHub pull requests stacked up since the summer? Best regards Gavin McNiff

2 2

[err] RFC
by Domagoj Saric 11 Jan '16

11 Jan '16

https://github.com/psiha/err README.md copy-paste: --------------------------------------------- err - yet another take on C++ error handling. We have throw and std::error_code, what more could one possibly want? --------------------------------------------- std::error_code&co tried to solve or at least alleviate the problem of overhead of using exceptions (in terms of both source code verbosity and binary code size&speed) with functions which need to report failures that need not be 'exceptional' depending on the context of the call (thereby requiring try-catch blocks that convert exceptions to 'result codes'). Unfortunately, the way it was finally implemented, std::error_code did not quite accomplish what it set out to do: • in terms of runtime efficiency: 'manual'/explicit EH (try-catch blocks) is no longer needed but the compiler still has to insert hidden EH as it has to treat the functions in question as still possibly throwing (in fact the implementation/codegen of functions which use std::error_code for error reporting becomes even fatter because it has to contain both return-on-error paths and handle exceptions) • in terms of source code verbosity: again, try-catch blocks are gone but separate error_code objects have to be declared and passed to the desired function. Enter boost::err: 'result objects' (as opposed to just result or error codes) which can be examined and branched upon (like with traditional result codes) or left unexamined to self-throw if they contain a failure result (i.e. unlike traditional result codes, they cannot be accidentally ignored). Thanks to latest C++ language features (such as r-value member function overloads) incorrect usage (that could otherwise for example lead to a result object destructor throwing during a stack-unwind) can be disallowed/detected at compile time. Discussions where the concept (or a similar one) was first concieved of and/or so far discussed: • http://boost.2283326.n4.nabble.com/system-filesystem-v3-Question-about-erro… • http://cpptips.com/fallible • https://github.com/ptal/std-expected-proposal • https://github.com/ptal/expected • https://github.com/adityaramesh/ccbase/blob/master/include/ccbase/error/exp… • http://stackoverflow.com/questions/14923346/how-would-you-use-alexandrescus… • https://svn.boost.org/trac/boost/wiki/BestPracticeHandbook#a8.DESIGN:Strong… • http://2013.cppnow.org/session/non-allocating-stdfuturepromise **************************************************************** For starter's, to reduce the length of the first post, I'll assume that everyone as at least somewhat familiar with similar/related proposals from Andrei Alexandrescu (std::expected) and Niall Douglas (std::monad) to which I gave links above. What, primarily, makes (Boost.)Err different from other proposals is the ability to (using latest C++ features) detect/distinguish between temporaries and 'saved' return values by using two different class templates (result wrappers), fallible_result (for rvalues) and result_or_error (for lvalues) and thus minimise or often completely eliminate any extra verbosity: If we had a function foo() that produces bar_t objects but can fail with an err_t, up till now we had two options: * bar_t foo() throw( err_t ); * optional<bar_t> foo( err_t & ); Err enables the library writer to write a single API and a single implementation: err::fallible_result<bar_t, err_t> foo(); where fallible_result is the class template that wraps temporaries/rvalues returned from functions and its member functions are all declared with && (i.e. callable only on rvalues) so you get a compiler error if you save it to an auto value and try to do anything with it. The two exceptions are the implicit conversion operators to: - bar_t, which will either return bar_t or throw err_t and which is used for the 'EH code path' bar_t my_bar( foo() ); - err::result_or_error<bar_t, err_t> which is used for the 'oldsk00l nothrow error code path' err::result_or_error<bar_t, err_t> maybe_bar( foo ); if ( maybe_bar ) { print( *maybe_bar ); } else { log( maybe_bar.error() ); } Also, if the fallible_result rvalue is left uninspected and contains an error its destructor will throw (which AFAICT should be safe considering it is an rvalue and no other exception can possibly be active at the same time) - this makes code that uses Err enabled libraries/APIs but relies on EH almost indistinguishable from 'classic EH' APIs (almost because the one difference that remains is with the immediate use of the return value: because of the wrapper class one can no longer write foo().do_something() but has to implicitly use the -> operator and write foo()->do_something() where the -> operator will check-and-throw if foo() did not succeed). To wrap up, this approach gives the user the immediate and fine grained control over which error handling mechanism he/she wants to use while allowing the developer to write a single API and implementation - AFAICT it is a no brainer replacement for <system_error>, it is less verbose and much more efficient ;-) ps. the small library @ https://github.com/psiha/err is by no means a finished product, it contains no tests or documentation but 'it works' (i.e. it is used in the, also upcoming, https://github.com/psiha/mmap)...I'm bringing it to public view for scrutiny, discussion and guidance lest I steer in the wrong direction ;) -- "What Huxley teaches is that in the age of advanced technology, spiritual devastation is more likely to come from an enemy with a smiling face than from one whose countenance exudes suspicion and hate." Neil Postman

4 20

Add Boost.Convert to the Trac
by Vicente J. Botet Escriba 11 Jan '16

11 Jan '16

Hi, I have requested this (https://svn.boost.org/trac/boost/ticket/11814) 6 weeks ago without response. Is anyone maintaining the Trac component? I see Doug Gregor, but I believe he is not actively working on Boost. Best, Vicente

2 2

[trac] boost 1.61
by Raffi Enficiaud 11 Jan '16

11 Jan '16

Hi all, Would it be possible to add 1.61 to the roadmap? Thanks, Raffi

2 1