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

[iostreams] basic_array_source: improper constructor argument
by Tatsuyuki Ishi 08 Apr '16

08 Apr '16

Since this is a 1-minute fix, I won't open any tickets: template<int N> basic_array_source(char_type (&)[N]); -> template<int N> basic_array_source(const char_type (&)[N]); Since iostream sources are read-only, this should be const.

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[Root Pointer] Seeking a Review Manager
by Phil Bouchard 08 Apr '16

08 Apr '16

Greetings, - "Root Pointer" is an alternative to the long unsolved problem of garbage collectors which lasted for more than 70 years! - Thanks to Paul A. Bristow for his help on the generation of the documentation which is now available at the following link: http://philippeb8.github.io/root_ptr/ (I apologize for the misplaced images in the rationale) - The library itself can be found here: https://github.com/philippeb8/root_ptr/ All examples and tests compile fine with BJAM with GCC and MSVC. - Also here is a quick overview on the benchmarks: Single threaded: unique_ptr (new): 43.2705 unique_ptr (make_unique): 42.4111 shared_ptr (new): 68.9101 shared_ptr (make_shared): 46.6575 shared_ptr (allocate_shared_noinit): 31.2334 root_ptr (new): 30.3701 Multi threaded: unique_ptr (new): 42.1397 unique_ptr (make_unique): 43.4631 shared_ptr (new): 76.4543 shared_ptr (make_shared): 76.6611 shared_ptr (allocate_shared_noinit): 81.9926 root_ptr (new): 66.3417 - An example of its usage can be seen here: https://github.com/philippeb8/root_ptr/blob/master/example/t100_test1.cpp We can see in the aforementioned link that outputting part of a complex graph, cyclic or not, can be done in the following simple way: cout << "Mind dump:" << endl; cout << * t100 << endl; cout << "Searching for: \"einstein\"" << endl; if (node_ptr<neuron_base> p = t100->search("einstein")) cout << p->sort().unique() << endl; cout << "Searching for: \"graviton\"" << endl; if (node_ptr<neuron_base> p = t100->search("graviton")) cout << p->sort().unique() << endl; Sincerely yours, -Phil

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[clang][preprocessor] Testing of clang emualting the VC++ preprocessor on Windows
by Edward Diener 07 Apr '16

07 Apr '16

I have made local changes in the Boost preprocessor config.hpp on the 'develop' branch to have clang's emulation of the non-standard VC++ preprocessor act like the VC++ preprocessor as far as Boost PP is concerned. Boost PP has a large number of workarounds for VC++ without which Boost PP preprocessor code would not work when compiling using any version of VC++. I have tested the usual compilers extensively to make sure they are unaffected by these changes as well as the normal clang-linux implementation. Everything remains the same for these compilers with my changes so I am assured the changes will not affect any other compiler implementation. I was able to test both clang-3.8 and the latest build of clang, which is clang-3.9, by invoking clang-cl. My user-config.jam file for these entries looks like: using clang-win : 3.8 : SomePath/clang-cl : <compatibility>vc12 using clang-win : 3.9 : SomePath/clang-cl : <compatibility>vc14 By passing toolset=clang-win-3.8 or toolset=clang-win-3.9 I was able to successfully test these implementations against the Boost PP test code. There are quite a few failures in this clang emulation of the VC++ preprocessor when tested against the preprocessor test code. In fact testing clang emulation of VC++ preprocessor when I don't treat clang as VC++ in Boost PP, but as its normal C++ standard conforming preprocessor, still fails a few cases but far less than when clang is treated as VC++ in Boost PP. Needless to say when invoking clang-linux, which tests the normal clang implementation whether on Windows or Linux, there are no failures in the Boost PP tests. I am perfectly willing to push my changes to 'develop' for the preprocessor. The changes are essentially just in the Boost PP config.hpp file, which sets macros which control the compiler workarounds in Boost PP. As I have previously stated I am not personally willing to try to figure out or report to clang why their VC++ preprocessor emulation in Boost PP is failing, but others who are interested can do so if they wish. My personal reasons for this is that I think it is a very bad thing to attempt to replicate an already flawed C++ preprocessor in another compiler in general code. I also have spent enough time working with the VC++ preprocessor trying to find workarounds for its non-standard behavior that I do not want to do so for another preprocessor which attempts to be non-standard. I posted this to alert others to my plans to update Boost PP on 'develop' with this change, in case anybody is greatly opposed to it or wants to discuss it further. The change will not affect any other compiler but clang in VC++ preprocessor emulation mode. Unless I hear objections etc. I plan to push my update within the next day although I will wait awhile for any replies to this post.

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New libraries are missing in library list
by Antony Polukhin 07 Apr '16

07 Apr '16

Hi, Seems that new libraries (Compute, DLL, Hana, Metaparse) are not available from pages http://www.boost.org/doc/libs/1_61_0_b1/ and http://www.boost.org/doc/libs/1_61_0/. Please, could someone fix that? -- Best regards, Antony Polukhin

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Nasty compile time reflection and iteration for POD types using C++14 without macro
by Antony Polukhin 07 Apr '16

07 Apr '16

Hello, I've come up with a trick that may be useful in Boost.Hana, Boost.Serialization or some other libraries. Here's a small motivating example: #include <cstdio> #include <boost/type_index.hpp> #include "magic.hpp" struct foo { unsigned char i0; unsigned int i1; unsigned short i2; unsigned long long i3; unsigned char ar[2]; int q; std::size_t w; int* p1; const void* p2; int const**const**** p_crazy; const double d; }; template <std::size_t I, class T> void print(T& f) { printf( "%lu\t\t%s\n", (std::size_t)get(f), boost::typeindex::type_id<decltype(get(f))>().pretty_name().c_str() ); } int main() { foo f {10, 11, 12, 13, {14, 15}, 16, 17, 0, 0, 0, 30.0}; print<0>(f); print<1>(f); print<2>(f); print<3>(f); print<4>(f); print<5>(f); print<6>(f); print<7>(f); print<8>(f); print<9>(f); print<10>(f); print<11>(f); static_assert(tuple_size<foo>() == 12, "failed tuple size check"); } That example will output: 10 unsigned char 11 unsigned int 12 unsigned short 13 unsigned long long 14 unsigned char 15 unsigned char 16 int 17 unsigned long 0 int* 0 void const* 0 int const** const**** 30 double Core ideas: 1) We may detect the POD structure fields by the POD's constructor: template <std::size_t I> struct ubiq { std::size_t* ref_; template <class Type> constexpr operator Type() const noexcept { ref_[I] = type_to_id(identity<Type>{}); return Type{}; } }; template <class T, std::size_t... I> constexpr auto type_to_array_of_type_ids(std::size_t* types) noexcept -> decltype(T{ ubiq{types}... }) { return T{ ubiq{types}... }; } Here type_to_array_of_type_ids will return array with types via `types`, each element of array encodes some basic type. 2) Then we convert that array into an std::index_sequence<I...> and create a type with same layout as our POD type: template <std::size_t... I> constexpr auto as_tuple_impl(std::index_sequence<I...>) noexcept { return std::tuple< decltype( id_to_type(std::integral_constant<std::size_t, I>{}) )... >{}; } 3) Now we have a type with same layout, and we cast the structure to that type: template <std::size_t I, class T> decltype(auto) get(const T& val) noexcept { auto t = reinterpret_cast<const decltype(detail::as_tuple<T>())*>( std::addressof(val) ); return get(*t); } Drawbacks: * works for POD types only (could be possibly extended to trivial constructible type) * structures with non-default alignment are not supported * step 3) contains an UB, but even without that step we're still able to get field types of the POD type and fields count * current draft implementation does no support nested PODs (could be fixed easily) * current draft implementation works only on libc++ (could be fixed easily, requires reimplementing std::tuple) * there's no known to me way to make get<>() method constexpr * does not detect constness (because of that get<>() always returns const reference) Is there any interest in this feature? Sources https://github.com/apolukhin/magic_get/blob/master/magic2.cpp Online experiments can be done here: http://coliru.stacked-crooked.com/a/c33857e566e76ce2 -- Best regards, Antony Polukhin

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Boost 1.61.0 Beta 1
by Vladimir Prus 06 Apr '16

06 Apr '16

The first beta packages for 1.61.0 beta 1 are now available: http://boost.cowic.de/rc/boost_1_61_0_b1.zip http://boost.cowic.de/rc/boost_1_61_0_b1.7z http://boost.cowic.de/rc/boost_1_61_0_b1.tar.bz2 http://boost.cowic.de/rc/boost_1_61_0_b1.tar.gz There are no changes compared to RC2, expect for different names of the archives and different name of the top-level directory in the archives. The SHA256 checksums are as follows: 3f8888099ee6f62b412a13be916dead2bacbdd6d69e5afd5b6fea4bb738e5df4 boost_1_61_0_b1.7z 866941f0038b27fcc69ced1490b2dc5fa8d20f505d66b939a92a68ef194d1a6c boost_1_61_0_b1.tar.bz2 0b92c5fb5b91641409b9675b2fd11d3b3fa5f71dd986d3b5fb03da201bf55474 boost_1_61_0_b1.tar.gz 9dffe5ee7f5f7bf7695f5738c686e44bd266933e3ca68732b0de5520c3c82615 boost_1_61_0_b1.zip Signed list of checksums should be posted within 24 hours. As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. It was discovered that the .zip and .7z archives actually have LF line endings, at least in some places. Fixing this is not quite trivial, as Travis uses ancient version of Ubuntu and Git, and is not deemed critical, as most Windows editors handle LF just fine. We might do something for the final release, or might not. Thanks! -- The release managers

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[endian] Project not maintained
by Tatsuyuki Ishi 06 Apr '16

06 Apr '16

The endian library was going to support float in 1.58, but even 1.61 is going to release soon, there is no news about the feature. I'm not going to say, that this library should have been rejected, but since it's accepted, the maintainer should at least complete the work. And what's the situation now? The float point feature is overdue for 1 year. The project is almost like abandoned. Last commit 4 months ago. Even the library isn't completed. I hope the creator, Beman, to take responsibility about this library.

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[multiprecision][build] Massive unexplained failures in develop
by John Maddock 04 Apr '16

04 Apr '16

Can anyone help me understand why just about every multiprecision test on every platform is failing with link errors, for example: http://www.boost.org/development/tests/develop/developer/output/teeks99-09d… Note that it's complaining about a missing *object* file: I've checked, and the necessary source files are present in the repository, plus I've pulled those changes on to a virtual machine and everything builds fine locally. So there's something odd about the build when run from /status or what exactly? I'm hoping someone can spot something obvious here, or else the testers can tell me where the object file actually placed? Thanks, John.

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[build] How to use with clang on windows?
by John Maddock 03 Apr '16

03 Apr '16

What's the correct way to configure clang on windows with current Boost.Build? If I use: using clang-win : 3.7 : "C:/Progra~2/MICROS~4.0/VC/Clang 3.7/bin/x86/clang.exe" : <cxxflags>-std=c++11 <compatibility>vc14 ; to configure the clang that ships with VC14 I see: compile-c-c++ ..\..\..\bin.v2\libs\smart_ptr\test\shared_ptr_basic_test.test\clang-vc14-win-3.7\debug\shared_ptr_basic_test.obj clang.exe: error: no such file or directory: '/Od' clang.exe: error: no such file or directory: '/Ob0' clang.exe: error: no such file or directory: '/W3' clang.exe: error: no such file or directory: '/GR' clang.exe: error: no such file or directory: '/MDd' clang.exe: error: no such file or directory: '/Zc:forScope' clang.exe: error: no such file or directory: '/Zc:wchar_t' clang.exe: error: no such file or directory: '/wd4675' clang.exe: error: no such file or directory: '/EHs' Same errors with the llvm clang-3.9. On the other hand if I initialize with: using clang : : "C:/Progra~2/LLVM/bin/clang.exe" : <cxxflags>-std=c++14 <compatibility>vc14 <cxxflags>-fms-compatibility-version=19.00.22609 ; Then this sort of works for llvm clang, but not the msvc one (can't find c2.exe), but the compiler is identified as "clang-linux" and I see: LINK : warning LNK4044: unrecognized option '/-start-group'; ignored LINK : warning LNK4044: unrecognized option '/Bstatic'; ignored LINK : warning LNK4044: unrecognized option '/Bdynamic'; ignored LINK : warning LNK4044: unrecognized option '/-end-group'; ignored Plus some linker errors such as: yield_k_test.obj : error LNK2019: unresolved external symbol __mm_pause referenced in function "void __cdecl boost::detail::yield(unsigned int)" (?yield@detail@boost@@YAXI@Z) Ideas? Thanks, John.

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Boost 1.61.0 open for fixes
by Vladimir Prus 02 Apr '16

02 Apr '16

The master branch is now open for bugfixes for 1.61.0. Please make sure that develop tests are healthy prior to merging. We're two weeks late relative to the plan, so further dates were also moved by two weeks in the calendar. -- The release managers

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[Trac][convert] Associate Vladimir as author of Boost.Convert
by Vicente J. Botet Escriba 01 Apr '16

01 Apr '16

Hi, I requested sometime ago to add convert to the Trac system. It was done, but it was associated to me as maintainer. Please, could someone assign it to Vladimir Batov Vladimir, I guess you need to give your use in name. Best, Vicente Convert <http://www.boost.org/doc/libs/1_60_0/libs/convert/> An extendible and configurable type-conversion framework. Author(s) Vladimir Batov First Release 1.59.0

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Coroutine2 examples - Cannot link properly.
by Carlos Ferreira 01 Apr '16

01 Apr '16

Hello to all. I'm having trouble in compiling the coroutine2 examples. For the fibonacci example, the following linking error occurs: /usr/include/boost/coroutine2/detail/pull_control_block.ipp:62: undefined reference to `boost::context::execution_context::current()' Now, I know that I have to link against boost context, something that I'm already doing, but for some reason, it is not enough. Can anyone help me with this? Thank you. -- Carlos Miguel Ferreira Researcher at Telecommunications Institute Aveiro - Portugal Work E-mail - cmf(a)av.it.pt Skype & GTalk -> carlosmf.pt(a)gmail.com LinkedIn -> http://www.linkedin.com/in/carlosmferreira

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