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Re: [Boost-users] iterator_facade Boost 1.57
by Matei David 07 Nov '14

07 Nov '14

On Tue, 04 Nov 2014 14:07:09 +0000 (UTC) gast128 wrote: > Dear all, > > Just trying out 1.57, since we are already 5 releases behind due to > all kinds of compilation errors with Boost and our software. Below > simplified code doesn't compile on vs2010: > > template <typename DerivedType> > struct IteratorFacade : public boost::iterator_facade<DerivedType, > int, std::random_access_iterator_tag> > { > typedef boost::iterator_facade<DerivedType, int, > std::random_access_iterator_tag> base; > > IteratorFacade (); > virtual ~IteratorFacade (); > > friend class boost::iterator_core_access; > > reference dereference () const; > }; > > struct MyIteratorFacade : IteratorFacade<MyIteratorFacade> > { > }; > > What do I wrong? Hi, I'm gcc 4.9.1 on Ubuntu 14.04. The reason this doesn't compile is that the "reference" typedef is contained in the glue class boost::iterator_facade, which is a base class of IteratorFacade<MyIteratorFacade>. When you write "reference" inside the later, the name is not being looked up in the base class. So you should write: typename base::reference dereference() const; If you want to use "reference" in many places in IteratorFacade<>, pull the typedef from its base with: typedef typename base::reference reference; or, if using C++11: using typename base::reference; Note: whether you pull it up or not, you can always get the typedef as IteratorFacade<...>::reference, or MyIteratorFacade::reference in your case. (See the example below, where I'm not pulling it up, but I can still find it.) I would also add the observation that your construct creates an unusual derivation. Usually, the iterator class you want to define has boost::iterator_facade as its direct base. In your case, boost::iterator_facade is the base of the base of your iterator class (so, 2 levels down): MyIteratorFacade : IteratorFacade<MyIteratorFacade> : boost::iterator_facade<MyIteratorFacade, ...> I'm not sure this would cause any problems, just be on the lookout for missing constructors. For example, this compiles just fine for me: #include <type_traits> #include <boost/iterator/iterator_facade.hpp> struct MyIteratorFacade : public boost::iterator_facade<MyIteratorFacade, int, std::random_access_iterator_tag> { typedef boost::iterator_facade<MyIteratorFacade, int, std::random_access_iterator_tag> base; MyIteratorFacade (); virtual ~MyIteratorFacade (); friend class boost::iterator_core_access; typename base::reference dereference() const; }; static_assert(std::is_same< MyIteratorFacade::value_type, int >::value, "MyIteratorFacade::value_type != int"); static_assert(std::is_same< MyIteratorFacade::reference, int& >::value, "MyIteratorFacade::reference != int&"); static_assert(std::is_same< MyIteratorFacade::pointer, int* >::value, "MyIteratorFacade::pointer != int*"); static_assert(std::is_same< std::iterator_traits<MyIteratorFacade>::value_type, int >::value, "iterator_traits<MyIteratorFacade>::value_type != int"); static_assert(std::is_same< std::iterator_traits<MyIteratorFacade>::reference, int& >::value, "iterator_traits<MyIteratorFacade>::reference != int&"); static_assert(std::is_same< std::iterator_traits<MyIteratorFacade>::pointer, int* >::value, "iterator_traits<MyIteratorFacade>::pointer != int*"); I compile with: g++ -Wall -Wextra -pedantic -std=c++11 -I${BOOST_INCLUDE_1_57} -c (I'm only using c++11 for static_assert.) M

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Boost.Python C++ pointer object to python: Attribute does not exist.
by Christoff Kok 07 Nov '14

07 Nov '14

Hi, I'm struggling with the following issue in a boost.python implementation: I have a list of std::shared_ptr in C++, I am accessing this list from Python. - When I access an element in the list, the elements does not have any attributes apparently. I get an error trying to access an attribute, hasattr returns false on the attribute, but dir informs me that it exist. - When I change the C++ implementation from shared_ptr to raw ptr's everything works as expected. - I want to use shared_ptrs for what I feel: obvious reasons. Below is the C++ code and the Python code. ################### ### garage_ext.cpp ### ################### #include<memory> #include<vector> namespace boost { template<class T> T* get_pointer(std::shared_ptr<T>& p){ return p.get(); }} struct Vehicle{ virtual ~Vehicle(){} friend bool operator==(const Vehicle& lhs, const Vehicle& rhs) { return true; } int testAttribute; }; struct Boat: public Vehicle { virtual ~Boat(){} friend bool operator==(const Boat& lhs, const Boat& rhs) { return true; } int testBoatAttribute; }; struct Garage { friend bool operator==(const Garage& lhs, const Garage& rhs) { return true; } std::vector<std::shared_ptr<Vehicle>>& vehicleList() { return m_VehicleList; } std::vector<std::shared_ptr<Boat>>& boatList() { return m_BoatList; } std::vector<std::shared_ptr<Vehicle>> m_VehicleList; std::vector<std::shared_ptr<Boat>> m_BoatList; }; #include <boost/python.hpp> #include <boost/python/suite/indexing/vector_indexing_suite.hpp> class BoatWrap : public Boat, public boost::python::wrapper<Boat> { public: static std::shared_ptr<Boat> cast(std::shared_ptr<Vehicle> const& v) { return std::dynamic_pointer_cast<Boat>(v); } }; BOOST_PYTHON_MODULE(garage_ext) { using namespace boost::python; class_<Garage>("Garage") .def("vehicleList", &Garage::vehicleList, return_internal_reference<1>()) .def("boatList", &Garage::boatList, return_internal_reference<1>()) ; class_<Vehicle, std::shared_ptr<Vehicle>,boost::noncopyable>("Vehicle", no_init) .def_readwrite("testAttribute", &Vehicle::testAttribute) ; class_<BoatWrap,std::shared_ptr<Boat>,bases<Vehicle>>("Boat") .def("cast", &BoatWrap::cast) .staticmethod("cast") .def_readwrite("testBoatAttribute", &Boat::testBoatAttribute) ; implicitly_convertible<std::shared_ptr<Boat>,std::shared_ptr<Vehicle>>(); class_<std::vector<std::shared_ptr<Vehicle>> >("stl_vector_Vehicle_ptr") .def(vector_indexing_suite<std::vector<std::shared_ptr<Vehicle>> >()); class_<std::vector<std::shared_ptr<Boat>> >("stl_vector_Boat_ptr") .def(vector_indexing_suite<std::vector<std::shared_ptr<Boat>> >()); } ##################### ### Python test code ### ##################### g = Garage() l = g.boatList() newboat = Boat() l.append(newboat) boatFromList = l[0] print(type(boatFromList)) print(str(hasattr(newboat,"testBoatAttribute"))) dir(boatFromList) # The following line throws the error. print(str(hasattr(boatFromList,"testBoatAttribute"))) I created a cast method for boat. If I cast l[0] to Boat using: boatFromList = Boat.cast(l[0]) print(str(hasattr(boatFromList,"testBoatAttribute"))) works. This is all very strange to me. It feels very buggy. Could someone please help me clarify the reason for this behavious? Regards, Christoff

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reference_wrapper on Boost 1.57
by gast128 06 Nov '14

06 Nov '14

This gives also a compilation error on vs2010: void F() { boost::reference_wrapper<float (* const)(float)> wrap(&cosf); //std::reference_wrapper<float (* const)(float)> wrap(&cosf); //ok } 1>KTestCuj2005June1.cpp(182): error C2248: 'boost::reference_wrapper<T>::reference_wrapper' : cannot access private member declared in class 'boost::reference_wrapper<T>' 1> with 1> [ 1> T=float (__cdecl *const )(float) 1> ] 1> C:\work sdk\boost_1_57_0\boost/core/ref.hpp(85) : see declaration of 'boost::reference_wrapper<T>::reference_wrapper' 1> with 1> [ 1> T=float (__cdecl *const )(float) 1> ] ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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Boost on Google+
by Vladimir Prus 06 Nov '14

06 Nov '14

Hi, I've created a Google+ community for Boost, and everybody is welcome to join here: https://plus.google.com/communities/106814259809358442744 I don't have any great plan here, but a lot of tech people are active on G+, so why not? -- Vladimir Prus CodeSourcery / Mentor Embedded http://vladimirprus.com

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boost 1.57: MS VS2008: unknown pragma in type_index.hpp
by Andreas Wehrmann 05 Nov '14

05 Nov '14

Hi! I've just compiled boost 1.57 with MS VS2008 x86 and this warning came all over the place: main\lib\boost_1_57_0\boost\type_index.hpp(37) : warning C4068: unknown pragma Still, the compilation went fine and everything seems to work as usual. It's just somewhat annoying because this warning pops up very often when I compile my applications. Regards, Andreas

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[Optional] Possible bug with VS2008
by dariomt＠gmail.com 05 Nov '14

05 Nov '14

Hi, The following minimal test case does not compile with VS2008 (using Boost 1.55) #include <boost/optional.hpp> struct A { int T; }; int main() { boost::optional<A> a; } The error is, edited for clarity: boost\optional\optional.hpp(479) : error C2523: 'A::~T' : destructor tag mismatch boost\optional\optional.hpp(479) : while compiling class template member function 'void boost::optional_detail::optional_base<T>::destroy_impl(boost::optional_detail::optional_base<T>::is_not_reference_tag)' with [ T=A ] boost\optional\optional.hpp(500) : see reference to class template instantiation 'boost::optional_detail::optional_base<T>' being compiled with [ T=A ] main.cpp(8) : see reference to class template instantiation 'boost::optional<T>' being compiled with [ T=A ] After much head-scratching, I found out the culprit: the name of the integer member!! The compiler confuses the name of member 'T' with the name of the template parameter 'T' when trying to invoke its destructor... The offending code is void destroy_impl ( is_not_reference_tag ) { get_ptr_impl()->T::~T() ; m_initialized = false ; } Given that I cannot change struct A, is there a way to fix this? Is this a compiler bug or a Boost.Optional bug? Thanks in advance!

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Spirit with UI Tools
by Philipp Kraus 05 Nov '14

05 Nov '14

Hello, I would like to create a small parser with Boost.Spirit. I have run the short examples and everything works well, so I would like to create my own LL grammar. In my case I need also for documentation a EBNF or something else and in the best case I can would like to create the EBNF first and transform this into the Spirit LL grammar code. Did you know any tools to do this? My first idea is to use AntLR to create the grammar but imho it creates a LR grammar. Can you recommend a tool to define the grammar structure and generate the Spirit code? Thanks a lot Phil

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Boost.Variant on Boost 1.57
by gast128 04 Nov '14

04 Nov '14

hello all, I get a compilation error with Boost.Operators and boost.Variant on vs2010: struct KFoo : boost::totally_ordered<KFoo> { }; bool operator<(const KFoo&, const KFoo&); bool operator==(const KFoo&, const KFoo&); void Foo() { boost::variant<KFoo> var; var.swap(var); } 1>C:\work sdk\boost_1_57_0\boost/variant/detail/move.hpp(60): error C2668: 'boost::swap' : ambiguous call to overloaded function 1> C:\work sdk\boost_1_57_0\boost/core/swap.hpp(54): could be 'void boost::swap<T,T>(T1 &,T2 &)' [found using argument-dependent lookup] 1> with 1> [ 1> T=T0, 1> T1=T0, 1> T2=T0 1> ] 1> C:\work sdk\boost_1_57_0\boost/variant/detail/move.hpp(44): or 'void boost::detail::variant::move_swap_fallback::swap<T,T>(T1 &,T2 &)' anyone?

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bjam building with error
by NtVisigoth 04 Nov '14

04 Nov '14

Hello, I cannot compile bjam.exe and I see error. I have googled and I see my trouble here: Name: "Build.bat does not autodetect msvc on 64-bit Windows when building bjam" URL: https://svn.boost.org/trac/boost/ticket/1091 To reproduce: 0. cd <boos libraries directory> 1. Start cmd.exe. 2. Then start bootstrap.bat I see: d:\projects\cpp-workspace\boost-libraries>bootstrap.bat Building Boost.Build engine \\Vim\\vim74\\";c:\portable-programs\adt-bundle-windows-x86_64\sdk\\platform-tools;c:\portable-progr ams\adt-bundle-windows-x86_64\sdk\\tools" was unexpected at this time. d:\projects\cpp-workspace\boost-libraries\tools\build\src\engine> What can I do to compile bjam ?

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problem with #include <boost/thread.hpp>
by Grison PG Pierre (External DEXIA-US) 04 Nov '14

04 Nov '14

Hello, I encounter a problem with the Thread library. The library works fine when I use it in a .exe project. It means it has been correctly built. Then I try to use the same library in an DLL project (so as to build a XLL object thanks to the XLW library). But as soon as I add the line #include <boost/thread.hpp> to my project, even if it compile without any problem, I get the following message when I debug my project through Excel: The file you are trying to open, "mylibrary.xll" is in a different format than specified by the file extension, Verify that the file is not corrupted [...]. Do you want to open the file now? And I can no more use my C++ functions in Excel. Do you have already encounter this problem? I use VS2010. I have tried both Multi-threaded Debug DLL (/MDd) and Multi-threaded DLL (/MD) options. My solution includes two other static libraries and also with the classic RunInterfaceGenerator XLW-project (the one which is executed when debugging). Regards, Pierre

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