Mailman 3 June 2008 - Cplusplus-sig

Including C++ classes
by Alex Hartog June 5, 2008

June 5, 2008

I am trying to include my own class in a C++ file which is used by boost. For some reason this does not work. I am certain this is not a C++ issue, because when I compile it without using boost, it does work. I am trying to include a simple class: "camera.h": #include <string> using namespace std; class camera { public: camera(); string imagePath; }; "camera.cpp": #include "camera.h" camera::camera(){ } "main.cpp": #include "camera.h" .... camera *c = new camera; .... When is use bjam, I get the following error message: E:\Studie\Bachelor Afstudeer Project\Code\voxel_coloring>bjam warning: Graph library does not contain optional GraphML reader. note: to enable GraphML support, set EXPAT_INCLUDE and EXPAT_LIBPATH to the note: directories containing the Expat headers and libraries, respectively. warning: skipping optional Message Passing Interface (MPI) library. note: to enable MPI support, add "using mpi ;" to user-config.jam. note: to suppress this message, pass "--without-mpi" to bjam. note: otherwise, you can safely ignore this message. Building Boost.Regex with the optional Unicode/ICU support disabled. Please refer to the Boost.Regex documentation for more information (don't panic: this is a strictly optional feature). ...patience... ...found 1176 targets... ...updating 2 targets... msvc.link.dll bin\msvc-9.0\debug\threading-multi\voxel_coloring_ext.pyd Creating library bin\msvc-9.0\debug\threading-multi\voxel_coloring_ext.lib an d object bin\msvc-9.0\debug\threading-multi\voxel_coloring_ext.exp voxel_coloring.obj : error LNK2019: unresolved external symbol "public: __thisca ll camera::camera(void)" (??0camera@@QAE@XZ) referenced in function "int __cdecl voxel_coloring2(class boost::python::list)" (? voxel_coloring2@@YAHVlist@python@ boost@@@Z) bin\msvc-9.0\debug\threading-multi\voxel_coloring_ext.pyd : fatal error LNK1120: 1 unresolved externals call "C:\Program Files (x86)\Microsoft Visual Studio 9.0 \VC\vcvarsall.ba t" x86 >nul link /NOLOGO /INCREMENTAL:NO /DLL /DEBUG /subsystem:console /out:"bin\msvc-9.0 \d ebug\threading-multi\voxel_coloring_ext.pyd" /IMPLIB:"bin\msvc-9.0 \debug\threadi ng-multi\voxel_coloring_ext.lib" /LIBPATH:"C:\python25\libs" @"bin\msvc-9.0 \de bug\threading-multi\voxel_coloring_ext.pyd.rsp" if %ERRORLEVEL% NEQ 0 EXIT %ERRORLEVEL% if exist "bin\msvc-9.0\debug\threading- multi\voxel_coloring_ext.pyd.mani fest" ( mt -nologo -manifest "bin\msvc-9.0\debug\threading- multi\voxel_color ing_ext.pyd.manifest" "-outputresource:bin\msvc-9.0\debug\threading- multi\voxel_ coloring_ext.pyd;2" ) ...failed msvc.link.dll bin\msvc-9.0\debug\threading- multi\voxel_coloring_ext.py d bin\msvc-9.0\debug\threading-multi\voxel_coloring_ext.lib... ...removing bin\msvc-9.0\debug\threading-multi\voxel_coloring_ext.lib ...failed updating 2 targets... If I just declare the class inside my main file, it does not give any problems. Can anyone help me with this problem?

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Nesting classes in boost::python
by Hans Meine June 4, 2008

June 4, 2008

Hi again, [note: this is not really about py++!] I wondered why py++ does not properly scope the nested classes. For example, in order to expose a nested class Foo::Bar, I use bp::scope in my own code like this: { scope foo( class_<Foo>("Foo") .def ... ); // normal class export decl. class_<Bar>("Bar") .def ... ; } // close scope foo (i.e. "Foo") The only reason why I could imagine that py++ does not do so is that AFAIK this breaks pickling (and possibly more things?), since Foo.Bar.__name__ is "Bar" in Python, which does not allow the pickle module to locate the class correctly. :-( This is the reason for the more general subject I chose, because this may deserve a discussion and/or fix within the BPL?! -- Ciao, / / /--/ / / ANS

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Py++: automatic type aliases
by Hans Meine June 4, 2008

June 4, 2008

Hi Roman, I looked at the py++ source code in order to fix the fact that my classes often get the wrong alias. For instance, template<class T> class Vector2 {}; typedef Vector2<short> ShortVector2; class SomeOther { typedef Vector2<short> Vector; // class-internal typedef! }; Since "Vector" is shorter than "ShortVector2", it wins in the "be_smart" mode. Also, I am getting W1047 (There are two or more classes that use same alias("Base"). ...) because I often typedef complex base classes to "Base" in order to refer to Base::foo. Can py++ be made more "intelligent" by discarding scoped typedefs if there are global ones? (I did not find where self.aliases is filled and how to fix this.) I will send a separate post for proper class nesting.. -- Ciao, / / /--/ / / ANS

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Re: [C++-sig] Pyplusplus: operators <</>> not supported?
by Hans Meine June 4, 2008

June 4, 2008

Hi Roman! Am Mittwoch, 04. Juni 2008 19:34:05 schrieben Sie: > Can you send me link to the shift operator definition within a class? I do not know any specific link to that. > It could be nice to see your class too. Attached is a simple variant of what I am doing. BTW: Note the double warning from py++ - the ugly-name-warning should IMHO be removed, since the operator is ignored anyway. > Take a look on next link, it will help you to modify generated code via > Py++: > http://language-binding.net/pyplusplus/documentation/inserting_code.html Thanks. I have already found that page in the meantime and successfully exploited the beauty of pygccxml. :-) -- Ciao, / / /--/ / / ANS

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Re: [C++-sig] Pyplusplus: operators <</>> not supported?
by Roman Yakovenko June 4, 2008

June 4, 2008

On Wed, Jun 4, 2008 at 2:56 PM, Hans Meine <meine(a)informatik.uni-hamburg.de> wrote: > Am Mittwoch, 04. Juni 2008 12:31:08 schrieb Roman Yakovenko: >> I found some definitions in MSDN for shift operators, but I didn't see >> how I can redefine them for class. >> Py++ has to distinct between shift and stream operators. > > BTW: currently I am using the following manual patch to add the operators: > .def( bp::self <<= bp::other< int >() ) > + .def( bp::self << bp::other< int >() ) > .def( bp::self == bp::self ) > .def( bp::self >>= bp::other< int >() ) > + .def( bp::self >> bp::other< int >() ) > > (Obviously, this would better be done with an appropriate py++ script, but > this is the first time I am using py++ and I do not yet know how this works.) Can you send me link to the shift operator definition within a class? It could be nice to see your class too. Take a look on next link, it will help you to modify generated code via Py++: http://language-binding.net/pyplusplus/documentation/inserting_code.html HTH -- Roman Yakovenko C++ Python language binding http://www.language-binding.net/

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Pyplusplus: operators <</>> not supported?
by Hans Meine June 4, 2008

June 4, 2008

Hi Roman, I have defined a class with shift operators: <<,>>,<<=,>>= Only the latter two in-place assignment-shift operators are recognized by py++. I have looked in the test suite and found pyplusplus_dev/unittests/data/operators_to_be_exported.hpp with the comment "Boost.Python does not support member operator<<", which indicates that you left them out for a purpose. However, it seems to work fine with boost 1.34.1 when I manually add the (self << int) def's, so maybe this is an old bug of boost::python which has been fixed since 2004? -- Ciao, / / /--/ / / ANS

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boost.python embedding tutorial doesn't work ?
by Aurélien MAIGNAN June 3, 2008

June 3, 2008

Hi I tried to executed the simple embedding tutorial from here : http://www.boost.org/doc/libs/1_35_0/libs/python/doc/tutorial/doc/html/pyth… here is my C++ code : Py_Initialize(); object main_module = import("__main__"); object main_dict = main_module.attr("__dict__"); try{ object result = exec("result = 5 + 5",main_dict); int five_squared = extract<int>(main_dict["result"]); cout<<"extract value : "<<five_squared<<endl; cin>>ij; } catch(error_already_set){ PyErr_Print(); cin>>ij; } doesn't work here is the python exception printed : Traceback (most recent call last): File "<string>", line 1, in <module> TypeError: 'NoneType' object does not support item assignment although other test work : Py_Initialize(); object main_module = import("__main__"); object main_dict = main_module.attr("__dict__"); try{ handle<> ignored((PyRun_String( "result = 5 ** 2" , Py_file_input , main_dict.ptr() , main_dict.ptr()) )); int five_squared = extract<int>(main_dict["result"]); cout<<"extract value : "<<five_squared<<endl; cin>>ij; } catch(error_already_set){ PyErr_Print(); cin>>ij; } => WORK and Py_Initialize(); object main_module = import("__main__"); object main_dict = main_module.attr("__dict__"); try{ object result = eval("5 + 5",main_dict); int five_squared = extract<int>(result); cout<<"extract value : "<<five_squared<<endl; cin>>ij; } catch(error_already_set){ PyErr_Print(); cin>>ij; } => WORK TOO thanks, Aurélien MAIGNAN

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How to officially wrap a pointer into boost::python::object?
by Hans Meine June 3, 2008

June 3, 2008

Hi! This seems to be such a simple task: Given a (e.g factory) function that wants to return a new object as boost::python::object, what is the correct code? For instance: boost::python::object myFactory() { Foo *result = new Foo(); boost::python::object pyresult = ..... result .....; // <- PLEASE FILL IN // e.g. set python attribute on pyresult.. return pyresult; } As far as I know, something like this was in the tutorial in the past, but has been deleted without being reproduced in any other place I know of. What I am doing right now is a little bit clumsy: boost::python::object pyresult = boost::python::object( boost::python::detail::new_reference( // ugly: private/"detail" API boost::python::manage_new_object::apply<Foo *>::type()(result))); I have looked at the implementation of manage_new_object to find a nicer shortcut, which leads to a is_polymorphic-if branch using detail::wrapper_base_::owner or detail::make_owning_holder respectively. I refrained from using make_owning_holder directly, not only because it is also in the detail namespace, but also because of the second if-branch which I completely do not understand. Also, I would like to not take the detour via an intermediate PyObject * which has to be wrapped again; make_owning_holder suggests that using std::auto_ptr could be a way, but I am unsure if this works with the special-cased Intel5 and VC 6 Dinkum library and whether I may leave out the above is_polymorphic stuff. In the end, I would like to know a) what is the right way(tm) for common end users, b) where this is (prominently) documented, and c) what is the perfectly-fine-in-all-cases way for code that should eventually go into the BPL. -- Ciao, / / /--/ / / ANS

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Pyplusplus: Support for anonymous structs?
by Hans Meine June 3, 2008

June 3, 2008

Hi Roman, after reporting to Gustavo that pybindgen does not support unnamed structs, I tried pyplusplus and found the same (OK, not the same - pyplusplus gracefully skips the members with the two warnings "Py++ can not export unnamed variables" and "Py++ can not export unnamed classes"). Actually, there are two problems: 1) py++ generates the following code, which does not mention the "low" and "high" members wrapped in the struct: bp::class_< Word >( "Word" ) .def_readwrite( "word", &Word::word ); This should be "easy to fix" - py++ would need to descend into the struct and add .def_readwrite( "low", &Word::low ) .def_readwrite( "high", &Word::high ) However, the next problem is fatal: 2) boost::python::class_ only works for structs and classes, but not for unions. I am getting an error from is_polymorphic: /software/boost-1.34.1/include/boost-1_34/boost/type_traits/is_polymorphic.hpp: At global scope: /software/boost-1.34.1/include/boost-1_34/boost/type_traits/is_polymorphic.hpp: In instantiation of 'boost::detail::is_polymorphic_imp1<Word>::d1': /software/boost-1.34.1/include/boost-1_34/boost/type_traits/is_polymorphic.hpp:56: instantiated from 'const bool boost::detail::is_polymorphic_imp1<Word>::value' /software/boost-1.34.1/include/boost-1_34/boost/type_traits/is_polymorphic.hpp:91: instantiated from 'const bool boost::detail::is_polymorphic_imp<Word>::value' /software/boost-1.34.1/include/boost-1_34/boost/type_traits/is_polymorphic.hpp:96: instantiated from 'boost::is_polymorphic<Word>' /software/boost-1.34.1/include/boost-1_34/boost/mpl/if.hpp:67: instantiated from 'boost::mpl::if_<boost::is_polymorphic<Word>, boost::python::objects::polymorphic_id_generator<Word>, boost::python::objects::non_polymorphic_id_generator<Word> >' /software/boost-1.34.1/include/boost-1_34/boost/python/object/inheritance.hpp:65: instantiated from 'boost::python::objects::dynamic_id_generator<Word>' /software/boost-1.34.1/include/boost-1_34/boost/python/object/inheritance.hpp:72: instantiated from 'void boost::python::objects::register_dynamic_id(T*) [with T = Word]' /software/boost-1.34.1/include/boost-1_34/boost/python/object/class_metadata.hpp:97: instantiated from 'void boost::python::objects::register_shared_ptr_from_python_and_casts(T*, Bases) [with T = Word, Bases = boost::python::bases<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_>]' /software/boost-1.34.1/include/boost-1_34/boost/python/object/class_metadata.hpp:225: instantiated from 'static void boost::python::objects::class_metadata<T, X1, X2, X3>::register_aux2(T2*, Callback) [with T2 = Word, Callback = boost::integral_constant<bool, false>, T = Word, X1 = boost::python::detail::not_specified, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' /software/boost-1.34.1/include/boost-1_34/boost/python/object/class_metadata.hpp:219: instantiated from 'static void boost::python::objects::class_metadata<T, X1, X2, X3>::register_aux(void*) [with T = Word, X1 = boost::python::detail::not_specified, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' /software/boost-1.34.1/include/boost-1_34/boost/python/object/class_metadata.hpp:205: instantiated from 'static void boost::python::objects::class_metadata<T, X1, X2, X3>::register_() [with T = Word, X1 = boost::python::detail::not_specified, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' /software/boost-1.34.1/include/boost-1_34/boost/python/class.hpp:496: instantiated from 'void boost::python::class_<T, X1, X2, X3>::initialize(const DefVisitor&) [with DefVisitor = boost::python::init<mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_, mpl_::void_>, W = Word, X1 = boost::python::detail::not_specified, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' /software/boost-1.34.1/include/boost-1_34/boost/python/class.hpp:629: instantiated from 'boost::python::class_<T, X1, X2, X3>::class_(const char*, const char*) [with W = Word, X1 = boost::python::detail::not_specified, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' foomodule.cxx:26: instantiated from here /software/boost-1.34.1/include/boost-1_34/boost/type_traits/is_polymorphic.hpp:28: error: base type 'Word' fails to be a struct or class type -- Ciao, / / /--/ / / ANS

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ANNOUNCE: PyBindGen 0.8
by Gustavo Carneiro June 3, 2008

June 3, 2008

The other day I released PyBindGen 0.8. Main news is that it features a new experimental header file scanner based on pygccxml (i.e., it's similar to py++ in scope, if not in maturity, but does not use boost.pythonunderneath). == What == PyBindGen is a Python module that is geared to generating C/C++ code that binds a C/C++ library for Python. It does so without extensive use of either C++ templates or C pre-processor macros. It has modular handling of C/C++ types, and can be easily extended with Python plugins. The generated code is almost as clean as what a human programmer would write, and does not depend on any library or header files besides Python itself. == Where == https://launchpad.net/pybindgen/ == NEWS == - Support C++ instance attributes through getter/setter methods - Support functions as methods of C++ classes - Support the PyObject* type - Support unsigned int, C strings (char*) (from Mark Lee) - Add basic support for enum types - New experimental automatic module generator based on C/C++ header file scanner and annotations in comments, using pygccxml - Some bug fixes -- Gustavo J. A. M. Carneiro INESC Porto, Telecommunications and Multimedia Unit "The universe is always one step beyond logic." -- Frank Herbert

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