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Looping through variadic macro arguments
by Florian Lindner 31 Mar '16

31 Mar '16

Hello, I have this macro: #define vmacro(expr, ...) \ cout << "n macro = " << BOOST_PP_VARIADIC_SIZE(__VA_ARGS__) << endl; \ cout << BOOST_PP_VARIADIC_ELEM(0, __VA_ARGS__) << endl; \ cout << BOOST_PP_VARIADIC_ELEM(1, __VA_ARGS__) << endl; \ for (int i = 0; i < BOOST_PP_VARIADIC_SIZE(__VA_ARGS__); i++) { \ cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ } The VARIADIC_SIZE is correct and I can access elements using BOOST_PP_VARIADIC_ELEM as long as I use a literal. The loop body produces error messages when compiling. BOOST_PP_VARIADICS is 1. The goal is to concatenate all variadic macro arguments to a string. If there a more clever solution, I'm very eager to hear them. Thanks! Florian ERROR MESSAGES: % clang++ -std=c++11 -g3 -rdynamic -ldl test.cpp test.cpp:154:3: error: expected expression vmacro(4, 5, 6); ^ test.cpp:120:26: note: expanded from macro 'vmacro' cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ ^ /usr/include/boost/preprocessor/variadic/elem.hpp:26:101: note: expanded from macro 'BOOST_PP_VARIADIC_ELEM' # define BOOST_PP_VARIADIC_ELEM(n, ...) BOOST_PP_CAT(BOOST_PP_VARIADIC_ELEM_, n)(__VA_ARGS__,) ^ 1 error generated. g++ -std=c++11 -g3 -rdynamic -ldl test.cpp In file included from test.cpp:9:0: test.cpp: In function 'void f(int)': test.cpp:120:26: error: expected primary-expression before ')' token cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ ^ test.cpp:154:3: note: in expansion of macro 'vmacro' vmacro(4, 5, 6); ^ test.cpp:120:26: error: 'BOOST_PP_VARIADIC_ELEM_i' was not declared in this scope cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ ^ test.cpp:154:3: note: in expansion of macro 'vmacro' vmacro(4, 5, 6); ^

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Boost 1.61.0 Beta 1 Release Candidate 2
by Vladimir Prus 31 Mar '16

31 Mar '16

Second set of release candidates for 1.61.0 beta 1 are now available: http://boost.cowic.de/rc/boost_1_61_0_b1_rc2.zip http://boost.cowic.de/rc/boost_1_61_0_b1_rc2.tar.bz2 http://boost.cowic.de/rc/boost_1_61_0_b1_rc2.tar.gz http://boost.cowic.de/rc/boost_1_61_0_b1_rc2.7z 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 changes from RC1 are: * Top-level directory in the archive matches the name * Zip and 7z archives use CRLF line endings The known issues are: * Documentation build has some wrong-location, extra-files and broken-links issues. * There was a report of Boost.Context issue on OSX Release managers believe these issues are not blocking beta 1. The SHA1 checksums are as follows: 4d3c83d3a802d3dd12d4f2d516b3fcf076f6f6ba boost_1_61_0_b1_rc2.7z 8c6ac7326a3cabcabf6c7876052b73e0d41fc36d boost_1_61_0_b1_rc2.tar.bz2 e82b8ff7c3ad5b08c7dbeac1ea85fcf707a1cd4d boost_1_61_0_b1_rc2.tar.gz 7292e8fdac0566fe098a60a197a5722d381842d3 boost_1_61_0_b1_rc2.zip The SHA256 checksums are as follows: bc8341bfb8c6621319ad9eb732179fc7ec4da35c3cefc31b613f83ec3df10361 boost_1_61_0_b1_rc2.7z c0f06c78c195af9079773a2b250674244f1899ec81e84d5455f0761f1d888a16 boost_1_61_0_b1_rc2.tar.bz2 400fa0949aa201d993bf116461365e5d44904a3f8db6412f4f40f2b4ab490405 boost_1_61_0_b1_rc2.tar.gz d75688ecad601303dda2658e9a3d06f406dd4dc8e2c13c36bdadcac0a11dcffa boost_1_61_0_b1_rc2.zip Thanks! -- The release managers

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Encountering an issue trying to compile on OS X 10.11.4
by Brian Krisler 29 Mar '16

29 Mar '16

Hi, I am trying to compile a package that utilizes boost libraries, and the compilation fails. This is on OS X El Capitan, with clang version: 7.3.0.7030029. Is this a known issue, and is there a work around? In file included from /opt/local/include/boost/signals2/slot_base.hpp:18: /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:42:54: error: reference to 'weak_ptr' is ambiguous template<typename T> struct weak_ptr_traits<std::weak_ptr<T> > ~~~~~^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:5035:29: note: candidate found by name lookup is 'std::__1::weak_ptr' class _LIBCPP_TYPE_VIS_ONLY weak_ptr ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:25:30: note: candidate found by name lookup is 'std::weak_ptr' template<typename T> class weak_ptr; ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:42:33: error: redefinition of 'weak_ptr_traits<weak_ptr<type-parameter-0-0> >' template<typename T> struct weak_ptr_traits<std::weak_ptr<T> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:38:33: note: previous definition is here template<typename T> struct weak_ptr_traits<boost::weak_ptr<T> > ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:54:56: error: reference to 'shared_ptr' is ambiguous template<typename T> struct shared_ptr_traits<std::shared_ptr<T> > ~~~~~^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:3847:29: note: candidate found by name lookup is 'std::__1::shared_ptr' class _LIBCPP_TYPE_VIS_ONLY shared_ptr ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:24:30: note: candidate found by name lookup is 'std::shared_ptr' template<typename T> class shared_ptr; ^ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:54:33: error: redefinition of 'shared_ptr_traits<shared_ptr<type-parameter-0-0> >' template<typename T> struct shared_ptr_traits<std::shared_ptr<T> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /opt/local/include/boost/signals2/detail/foreign_ptr.hpp:50:33: note: previous definition is here template<typename T> struct shared_ptr_traits<boost::shared_ptr<T> > ^ 4 errors generated. Thanks Brian

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Build console_test_runner.cpp in boost-1.60.0
by Sergiy Tkachuk 29 Mar '16

29 Mar '16

Hello, I downloaded sources boost_1_60_0.zip from boost.org I have built boost libraries. After this I tried to build console_test_runner.cpp located at \libs\test\tools\console_test_runner\src\console_test_runner.cpp of boost_1_60_0.zip. I run following command: ..\..\..\..\b2 toolset=msvc-14.0 address-model=64 variant=release debug-symbols=on I run it from the folder \libs\test\tools\console_test_runner\ I got errors, I tried to investigate them. It appears that console_test_runner.cpp contains following line: #include <boost/test/utils/runtime/cla/named_parameter.hpp> I tried to search boost folder for files "named_parameter*.*". I found html-files only. Then I checked Boost.Test repo at https://github.com/boostorg/test, rev. 36c5fe6a5604d0277f6d6a4cf167f95c38095c3c I also didn't found "named_parameter*.*" How can I obtain console_test_runner.exe from console_test_runner.cpp? I am not an expert in building boost, I just need working binaries. Thank you, -- Best wishes, Sergiy

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LynxOS
by Miller, Caleb R 28 Mar '16

28 Mar '16

Has anyone ever used boost with LynxOS? In particular LynxOS-178 using ppc? Thanks, Caleb Caleb R. Miller 314-232-5633 The Boeing Company

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Re: [Boost-users] Boost.Serialization how to use serialize without nvp
by Bjorn Reese 27 Mar '16

27 Mar '16

On 03/23/2016 12:45 PM, gast128 wrote: > We want archives the same for debug and release. So I tried a couple of things: > * use primitive_type: This doesn't work if the type T is a string. Basically > it doesn't come in the 'load(std::wstring &ws)' anymore, since it now routes > to operator<< and then all kinds of nasty thing happens for xml archives. I do not have a solution for you, but I wanted to voice my support for a new level type to ignore a nesting level (but not its content) during serialization.

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ptree json parser is not bidirectionnal
by Sébastien Gallou 25 Mar '16

25 Mar '16

Hi all, I experience a strange behavior of parsing non-JSON data with JSON parser. Take this example : boost::property_tree::ptree m_tree; > // Non-JSON to ptree using JSON parserstd::istringstream is("1"); // Simple value, non-JSON > boost::property_tree::json_parser::read_json(is, m_tree); // ==> No exception ! > // ptree back to JSONstd::ostringstream buf; > boost::property_tree::json_parser::write_json(buf, m_tree, false); // ==> Exception > > Unserializing non-JSON value using JSON parser doesn't raise exception. If you try to serialize the resulted ptree, you now got an exception. Is this behavior normal ? In this case, is there an easy and light mean to check that input value is JSON formatted (Regex ?) ? Thanks for your help, S. Gallou

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How to add child tree into an existing tree.
by Anil Jangam 24 Mar '16

24 Mar '16

Hi, I have the following property tree. propset1 { prop1 2 prop2 5 prop3 60 prop4 7 } I am trying to add couple of child trees to this so that the resulting property tree would look like below. propset1 { prop1 2 prop2 5 prop3 60 prop4 5 childset1 { child1prop1 4 child1prop1 6 child1prop1 9 } childset2 { child2prop1 2 child2prop1 6 child2prop1 7 } } I wrote the following code. // Add General config pt::ptree propset1; propset1.put("propset1.prop1", 2); propset1.put("propset1.prop2", 5); propset1.put("propset1.prop3", 60); propset1.put("propset1.prop4", 7); // Add childset1 config pt::ptree childset1; childset1.add("child1prop1", 4); childset1.add("child1prop2", 6); childset1.add("child1prop3", 9); propset1.add_child("childset1", childset1); // Add childset2 config pt::ptree childset2; childset2.add("child2prop1", 2); childset2.add("child2prop2", 6); childset2.add("child2prop3", 7); propset1.add_child("childset2", childset2); However the above code is resulting into below property tree. propset1 { prop1 2 prop2 5 prop3 60 prop4 5 childset1 { child1prop1 4 child1prop1 6 child1prop1 9 } } propset1 { prop1 2 prop2 5 prop3 60 prop4 5 childset2 { child2prop1 2 child2prop1 6 child2prop1 7 } } Can someone please suggest what is correct use of API? /anil

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Selecting function overloads with boost::overload()
by Reza Jahanbakhshi 23 Mar '16

23 Mar '16

First a little bit of background. Recently I've been using boost.python and I noticed choosing a specific function overload is kind of messy when defining class interfaces or free functions. Consider the following functions and member functions: void fn(int i, float f); int fn(const std::string& str); float car::method(); void car::method(int i, double d); According to boost.python documentation we can add these function using either of following constructs: void (*fn1)(int, float) = fn; int (*fn2)(const std::string&) = fn; def("fn", fn1); def("fn", fn2); float (car::*method1)() = &car::method; void (car::*method2)(int, double) = &car::method; .def("method", method1) .def("method", method2) or to avoid those intermediate variables we can do it directly: def("fn", (void (*)(int, float))fn); def("fn", (int (*)(const std::string&))fn); .def("method", (float(car::*)())&car::method) .def("method", (void (car::*)(int, double))&car::method) Which in my opinion is not readable enough. So I wrote a small utility to make it a little bit more readable. For example: def("fn", overload<void(int, float)>(fn)); def("fn", overload<int(const std::string&)(fn)); .def("method", overload<float()>(&car::method)); .def("method", overload<void(int, double)>(&car::method)); Notice how I gave the desired signature to the overload function and it will choose that exact overload for me. It's not only limited to boost.python and we can use it wherever we need to select a specific overloaded function. For example: auto f = overload<void(int, float)>(fn); Of course it's just a syntactic sugar and you might not find it improving anything at all but in my case it helped my code readability somehow. Now my question. I pasted the whole thing here. As for non-member functions I could implement it relying only on C++11 variadic templates. But for member functions I couldn't find a way to do it without boost.preprocess and using only C++11 variadic template. Here is the full code tested with GCC 5.3.1 (std=C++11), Clang 3.7.0 (std=C++11) and MSVC2015 #include <type_traits> #include <boost/mpl/vector.hpp> #include <boost/preprocessor/arithmetic/inc.hpp> #include <boost/preprocessor/punctuation/comma_if.hpp> #include <boost/preprocessor/repetition.hpp> namespace boost { namespace detail { template <typename SignatureType> struct fn_signature; template <typename ResultType, typename... ArgType> struct fn_signature<ResultType(ArgType...)> { using result_type = ResultType; using arg_type = boost::mpl::vector<ArgType...>; static const std::size_t arg_count = sizeof...(ArgType); using type = ResultType(*)(ArgType...); }; template <typename ClassType, typename SignatureType> struct memfn_signature; template <typename ClassType, typename ResultType, typename... ArgType> struct memfn_signature<ClassType, ResultType(ArgType...)> { using type = ResultType(ClassType::*)(ArgType...); }; } // namespace detail template <typename SignatureType> typename detail::fn_signature<SignatureType>::type overload(typename detail::fn_signature<SignatureType>::type fn) { return fn; } #define BOOST_OVERLOAD_MAX_ARGS_COUNT 5 #define BOOST_OVERLOAD_PP_METHOD_OVERLOAD_ARGS(Z, N, C) BOOST_PP_COMMA_IF(N) typename std::enable_if<detail::fn_signature<SignatureType>::arg_count == C, typename boost::mpl::at_c<typename detail::fn_signature<SignatureType>::arg_type, N>::type>::type #define BOOST_OVERLOAD_PP_METHOD_OVERLOAD_IMPL(Z, N, _) \ template <typename SignatureType, typename ClassType> \ typename detail::memfn_signature<ClassType, SignatureType>::type overload(typename detail::fn_signature<SignatureType>::result_type(ClassType::*memfn)(BOOST_PP_REPEAT(N, BOOST_OVERLOAD_PP_METHOD_OVERLOAD_ARGS, N))) \ { \ return memfn; \ } BOOST_PP_REPEAT(BOOST_PP_INC(BOOST_OVERLOAD_MAX_ARGS_COUNT), BOOST_OVERLOAD_PP_METHOD_OVERLOAD_IMPL, _) #undef BOOST_OVERLOAD_PP_METHOD_OVERLOAD_IMPL #undef BOOST_OVERLOAD_PP_METHOD_OVERLOAD_ARGS #undef BOOST_OVERLOAD_MAX_ARGS_COUNT } // namespace boost The problem is I cannot find a way to force the overload resolution to pick the specific overload and also automatically deduce the ClassType template parameter at the same time. If the language let me to alias a variadic template parameter then it would be possible to do it. For example I could do this: template <typename ClassType, typename ResultType, typename... ArgType> struct memfn_signature<ClassType, ResultType(ArgType...)> { using type = ResultType(ClassType::*)(ArgType...); using result_type = ResultType; *using arg_type = ArgType...;* }; template <typename SignatureType, typename ClassType> typename detail::memfn_signature<ClassType, SignatureType>::type overload(typename detail::memfn_signature<SignatureType>::result_type (ClassType::*memfn)(typename detail::memfn_signature<SignatureType>::arg_type)) { return memfn; } Right now my preprocess implementation works with no problem but It's not a clean implementation. So is there any other way that I can do this. I appreciate your help.

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Boost.Serialization how to use serialize without nvp
by gast128 23 Mar '16

23 Mar '16

Hello all, we basically have a setup like this: #ifdef _DEBUG template <typename T> struct Wrapper { T m_value; }; #define HANDLE(T) Wrapper<T> #else #define HANDLE(T) T #endif We want archives the same for debug and release. So I tried a couple of things: * use primitive_type: This doesn't work if the type T is a string. Basically it doesn't come in the 'load(std::wstring &ws)' anymore, since it now routes to operator<< and then all kinds of nasty thing happens for xml archives. * overload serialize. This is also a failure, since it expects somehow a nvp, which I tried to circumvent since then there is a difference between archives in debug or release. Using 'is_wrapper' doesn't help either template <class Archive, typename T> void serialize(Archive& ar, Wrapper<T>& r, const unsigned int) { ar & r.m_value; // static assert in basic_xml_iarchive::load_override } somehow I must specify raw storage in the serialize function, but load_override and its siblings are all protected. Anyone?

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