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

[proto][variant] variant crashes proto expression
by Igor R 13 May '16

13 May '16

The following code is a slightly modified Proto calc2 example. Instead of doubles I use variant<int, double>, and the expression is just _1 = _2. This code triggers assertion in variant/detail/forced_return.hpp, so it looks like some variant instance gets messed up. It happens when the value returned from proto::eval(*this, ctx) is being copied. It can be reproduced both with MSVC and gcc, with Boost 1.60. Is there any workaround for this issue? Thanks. ////////////// #include <iostream> #include <boost/proto/proto_typeof.hpp> #include <boost/proto/core.hpp> #include <boost/proto/context.hpp> #include <boost/variant.hpp> namespace proto = boost::proto; using proto::_; typedef boost::variant<int, double> var_t; template<typename Expr> struct calculator_expression; // Tell proto how to generate expressions in the calculator_domain struct calculator_domain : proto::domain<proto::generator<calculator_expression> > {}; // Will be used to define the placeholders _1 and _2 template<int I> struct placeholder {}; // Define a calculator context, for evaluating arithmetic expressions // (This is as before, in calc1.cpp) struct calculator_context : proto::callable_context< calculator_context const > { // The values bound to the placeholders var_t d[2]; // The result of evaluating arithmetic expressions typedef var_t result_type; explicit calculator_context(const var_t &d1 = var_t(), const var_t &d2 = var_t()) { d[0] = d1; d[1] = d2; } // Handle the evaluation of the placeholder terminals template<int I> result_type operator ()(proto::tag::terminal, placeholder<I>) const { return d[ I - 1 ]; } }; // Wrap all calculator expressions in this type, which defines // operator () to evaluate the expression. template<typename Expr> struct calculator_expression : proto::extends<Expr, calculator_expression<Expr>, calculator_domain> { explicit calculator_expression(Expr const &expr = Expr()) : calculator_expression::proto_extends(expr) {} BOOST_PROTO_EXTENDS_USING_ASSIGN(calculator_expression<Expr>) // Override operator () to evaluate the expression var_t operator ()() const { calculator_context const ctx; return proto::eval(*this, ctx); } var_t operator ()(const var_t &d1) const { calculator_context const ctx(d1); return proto::eval(*this, ctx); } var_t operator ()(const var_t &d1, const var_t &d2) const { calculator_context const ctx(d1, d2); return proto::eval(*this, ctx); } }; // Define some placeholders (notice they're wrapped in calculator_expression<>) calculator_expression<proto::terminal< placeholder< 1 > >::type> const _1; calculator_expression<proto::terminal< placeholder< 2 > >::type> const _2; // Now, our arithmetic expressions are immediately executable function objects: int main() { BOOST_PROTO_AUTO(expr, _1 = _2); var_t a1(1), a2(2.5); expr(a1, a2); return 0; }

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[intrusive] crash with slist push_back
by Arpan Sen 12 May '16

12 May '16

Hi Boost Dev, Please consider the following code, this crashes with slist but works just fine if I replace slist with list. Also flat_map crashes but std::map works fine. Am I doing something gross or is there a bug here? #include <iostream> #include <boost/container/flat_map.hpp> #include <map> //#include <boost/intrusive/list.hpp> #include <boost/intrusive/slist.hpp> using namespace boost::intrusive; struct m : public slist_base_hook<> { int n; public: m(int k) : n(k) { } }; int main() { boost::container::flat_map<int, slist<m, cache_last<true> > > c1; std::map<int, slist<m, cache_last<true> > > c2; m* m1 = new m(22); c1[1].push_back(*m1); m* tt = new m(99); c2[1].push_back(*tt); } Regards Arpan

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Using thread_local with Boost.Thread
by Ruediger Berlich 11 May '16

11 May '16

Hi there, I am curious whether it would be possible to use C++11 thread_local instead of Boost's own TLS, while continuing to use Boost.Thread ? I assume that there will be problems if Boost falls back to native pthread ? Kind Regards, Beet

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Boost 1.61.0 Release Candidate 2
by Vladimir Prus 11 May '16

11 May '16

The second release candidates for the 1.61.0 release are now available at: http://boost.cowic.de/rc/boost_1_61_0_rc2.zip http://boost.cowic.de/rc/boost_1_61_0_rc2.7z http://boost.cowic.de/rc/boost_1_61_0_rc2.tar.bz2 http://boost.cowic.de/rc/boost_1_61_0_rc2.tar.gz The SHA256 checksums are as follows: fa1c34862b7ba8674ed6e064a14667a11830c6252f702d9458451834b74f7815 boost_1_61_0_rc2.7z a547bd06c2fd9a71ba1d169d9cf0339da7ebf4753849a8f7d6fdb8feee99b640 boost_1_61_0_rc2.tar.bz2 a77c7cc660ec02704c6884fbb20c552d52d60a18f26573c9cee0788bf00ed7e6 boost_1_61_0_rc2.tar.gz 02d420e6908016d4ac74dfc712eec7d9616a7fc0da78b0a1b5b937536b2e01e8 boost_1_61_0_rc2.zip The changes relative to RC1 are MSVC fixes for signals2 and graph libraries. 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. The signed list of checksums is also attached, signed with the following key: https://pgp.mit.edu/pks/lookup?op=get&search=0xDA472E8659753BA4 Key fingerprint C5F0 F367 AA66 616F B839 806E DA47 2E86 5975 3BA4 Thanks! -- The release managers

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[lockfree] _ENABLE_ATOMIC_ALIGNMENT_FIX for VS 2015 Update 2
by Stephan T. Lavavej 11 May '16

11 May '16

Hi, While running Boost.Lockfree's tests, one of our compiler devs encountered the following failure: freelist_test.cpp c:\wcfb01\binaries\x86chk\inc\atomic(659): error C2338: You've instantiated std::atomic<T> with sizeof(T) equal to 2/4/8 and alignof(T) < sizeof(T). Before VS 2015 Update 2, this would have misbehaved at runtime. VS 2015 Update 2 was fixed to handle this correctly, but the fix inherently changes layout and breaks binary compatibility. Please define _ENABLE_ATOMIC_ALIGNMENT_FIX to acknowledge that you understand this, and that everything you're linking has been compiled with VS 2015 Update 2 (or later). c:\wcfb01\binaries\x86chk\inc\atomic(669): note: see reference to class template instantiation 'std::_Atomic_base<_Ty,4>' being compiled with [ _Ty=boost::lockfree::detail::tagged_index ] e:\boost\boost\boost\lockfree\detail\freelist.hpp(608): note: see reference to class template instantiation 'std::atomic<boost::lockfree::detail::tagged_index>' being compiled e:\boost\boost\boost\lockfree\detail\freelist.hpp(609): note: see reference to class template instantiation 'boost::lockfree::detail::fixed_size_freelist<T,NodeStorage>' being compiled call "C:\WCFB01\binaries\x86chk\bin\i386\vcvarsall.bat" x86 >nul cl /Zm800 -nologo @"..\bin.v2\libs\lockfree\test\freelist_test.test\msvc-latest\debug\threading-multi\freelist_test.obj.rsp" ...failed compile-c-c++ ..\bin.v2\libs\lockfree\test\freelist_test.test\msvc-latest\debug\threading-multi\freelist_test.obj... with the following type: class tagged_index { public: typedef boost::uint16_t tag_t; typedef boost::uint16_t index_t; protected: index_t index; tag_t tag; }; This is by design - your tagged_index has align 2, size 4, triggering the need for my atomic alignment fix. As the static_assert advises, your code needs to define _ENABLE_ATOMIC_ALIGNMENT_FIX in order to pass. If this has already been fixed in 1.61.0, then that's great (I haven't checked). Thanks, STL

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Getting started with boost in Codeblocks
by Karan Kapoor 11 May '16

11 May '16

Hi, This is Karan Kapoor,a 3rd year UG student at NSIT. Can somebody guide me how to get started with boost libraries while i am using codeblocks. Karan Kapoor

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Boost.Random subtract_with_carry doesn't like m == numeric_limits<result_type>::digits
by Billy O'Neal (VC LIBS) 10 May '16

10 May '16

Hello, Boost folks. I found a bug in subtract_with_carry_engine while fixing a bug in MSVC++'s implementation of the same, where m == numeric_limits<result_type>::digits. Consider the following: #include <stdlib.h> #include <stdio.h> #ifdef USE_BOOST #include <boost/random/subtract_with_carry.hpp> using namespace boost::random; #else #include <random> using namespace std; #endif template <typename Engine> typename Engine::result_type run_10k(Engine engine) { for (int i = 0; i < 9999; ++i) { engine(); } return engine(); } int main() { subtract_with_carry_engine<unsigned long long, 64, 10, 24> ull_swc; ull_swc.seed(0x12341234'00000000); printf("0x%016llX\n", run_10k(ull_swc)); } MSVC++ said: 0xFCF0A4776BA0A6A8 Libstdc++ says: 0x01316AEA3646F686 Libc++ says: 0x01316AEA3646F686 Boost 1.60.0/libc++ + Clang says: 0x69E18848FE1BD36D Boost 1.60.0/libstdc++ + g++ says: 0x1DD6C263C41EEED0 MSVC++'s bug was that we did the underflow check incorrectly resulting in the carry bit always being set if m == numeric_limits<result_type>::digits. I fixed that and MSVC++ will agree with libstdc++ and libc++ in the next update; but boost's behavior here is still strange. Hope that helps, Billy Robert O'Neal III SDE II - Visual C++ Libraries bion(a)microsoft.com

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[thread] API for getting/setting thread name in Boost?
by Bob Summerwill 10 May '16

10 May '16

I've also been working with an external developer which is getting Ethereum C++ working on Alpine Linux, as a statically linked executable using musl, rather than glibc. One rather confusing element was related to setting and getting thread names, which is the process of working through this issue, I find appears not to have made its way into either Boost or the C++11 standard library, though it must be a very common cross-platform use-case. https://github.com/ethereum/libweb3core/pull/73 https://github.com/ethereum/libweb3core/pull/73/files I've just added this comment-block, while fixing the issue: /// Set the current thread's log name. /// /// It appears that there is not currently any cross-platform way of setting /// thread names either in Boost or in the C++11 runtime libraries. What is /// more, the API for 'pthread_setname_np' is not even consistent across /// platforms which implement it. /// /// A proposal to add such functionality on the Boost mailing list, which /// I assume never happened, but which I should follow-up and ask about. /// http://boost.2283326.n4.nabble.com/Adding-an-option-to-set-the-name-of-a-bo… /// /// man page for 'pthread_setname_np', including this crucial snippet of /// information ... "These functions are nonstandard GNU extensions." /// http://man7.org/linux/man-pages/man3/pthread_setname_np.3.html /// /// Stack Overflow "Can I set the name of a thread in pthreads / linux?" /// which includes useful information on the minor API differences between /// Linux, BSD and OS X. /// http://stackoverflow.com/questions/2369738/can-i-set-the-name-of-a-thread-i… /// /// musl mailng list posting "pthread set name on MIPs" which includes the /// information that musl doesn't currently implement 'pthread_setname_np' /// https://marc.info/?l=musl&m=146171729013062&w=1 void setThreadName(std::string const& _n); Would I be right in assuming that this never happened? http://boost.2283326.n4.nabble.com/Adding-an-option-to-set-the-name-of-a-bo… If not, where can I log an issue to request that we revisit that? From what I can see, everybody is likely just cut-and-pasting much the same code for this functionality. http://stackoverflow.com/questions/10121560/stdthread-naming-your-thread Cheers, Bob Summerwill -- bob(a)summerwill.net

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[config] Boost and the Intel (Linux) compiler
by Bob Summerwill 10 May '16

10 May '16

I am a developer on the Ethereum C++ client ( https://github.com/ethereum/webthree-umbrella) and have been working with an external developer on adding support to the codebase for building with the Intel Compiler on Ubuntu. Here is the full log of pain :-) https://github.com/ethereum/webthree-umbrella/issues/396 We've already merged various changes, and we appear to be getting down to the real hard ones, which are now mainly clustered around build issues with boost::multiprecision and seeming limitations with the Intel compiler and Like so: /home/libweb3core/libdevcore/Base64.h(48): error: no suitable conversion function from "boost::multiprecision::number<boost::multiprecision::backends::cpp_int_backend<160U, 160U, boost::multiprecision::unsigned_magnitude, boost::multiprecision::unchecked, void>, boost::multiprecision::et_off>" to "unsigned int" exists unsigned r = (unsigned)(a - a / 36 * 36); // boost's % is broken ^ detected during instantiation of "std::string dev::toBase36(const dev::FixedHash<N> &) [with N=20UL]" at line 114 of "/home/libethereum/libethcore/ICAP.cpp" This appears to be the key observation: https://github.com/ethereum/webthree-umbrella/issues/396#issuecomment-20659… "In summary, the intel platform supports this "convert_to" member function, but does not support implicit conversion of boost multiprecision types" Has anybody worked with Boost and the Intel compiler who might have some further insight into whether there is some way in which the Intel compiler "warts" can be handed within Boost? Or are we stuck with these nasty diffs/workarounds? https://github.com/ethereum/libethereum/pull/224/files https://github.com/ethereum/libweb3core/pull/68/files Cheers, Bob Summerwill Developer, Ethereum Foundation -- bob(a)summerwill.net

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github issues tracking listing
by Vicente J. Botet Escriba 09 May '16

09 May '16

Hi, I would like to have the possibility to have github issues in my boost modules (thread/chrono/ratio). I see that Boost.Hana has its own issue list. What I need to do to add the possibility to add issues? Best, Vicente

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