Mailman 3 August 2006 - Cplusplus-sig

How argument passing works with boost python ?
by cbailly Aug. 15, 2006

Aug. 15, 2006

Hi, I have read tutorials/FAQS about boost python but still, I do not understand how arguments are passed and converted (automatically ?) to the C++ types... since the profile of the methods are not declared. For instance, in the Hello world example (from the tutorial) BOOST_PYTHON_MODULE(hello) { class_<World>("World") .def("greet", &World::greet) .def("set", &World::set) ; } "set" method takes a std::string argument (not declared). This is really a mystery... Is the std::string type compatible with the str type ? Where is the conversion made ?. What if the method set takes std::string & parameter instead ? Can somebody help me understand the mechanism for argument passing ? Thanks a lot, Chris -- Utilisant le client e-mail révolutionnaire d'Opera : http://www.opera.com/mail/

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boost-python link errors
by Qun Cao Aug. 15, 2006

Aug. 15, 2006

Hi Everyone, I ran into some linking problem when I try to use MSVC7 IDE to compile my python extension, I then tried to compile the getting_started1.cpp (located on boost_1_33\libs\python\example), the same link error happened. My .dsp file was copied from libs/python/build/VisualStudio.as instructed on the boost building and testing manual on http://www.boost.org/libs/python/doc/building.html#testing. The only change I made was to add python include and libs path. The errors are like this: Linking... Creating library .\../bin-stage/boost_python_debug.lib and object .\../bin-stage/boost_python_debug.exp getting_started2.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall boost::python::error_already_set::~error_already_set(void)" (??1error_already_set@python@boost@@UAE@XZ) referenced in function "public: virtual void * __thiscall boost::python::error_already_set::`scalar deleting destructor'(unsigned int)" (??_Gerror_already_set@python@boost@@UAEPAXI@Z) getting_started1.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall boost::python::error_already_set::~error_already_set(void)" (??1error_already_set@python@boost@@UAE@XZ) referenced in function "class std::ctype<char> const & __cdecl std::use_facet<class std::ctype<char> >(class std::locale const &)" (??$use_facet@V?$ctype@D@std@@@std@@YAABV?$ctype@D@0@ABVlocale@0@@Z) getting_started2.obj : error LNK2001: unresolved external symbol "public: virtual unsigned int __thiscall boost::python::objects::py_function_impl_base::max_arity(void)const " (?max_arity@py_function_impl_base@objects@python@boost@@UBEIXZ) getting_started1.obj : error LNK2019: unresolved external symbol "public: virtual unsigned int __thiscall boost::python::objects::py_function_impl_base::max_arity(void)const " (?max_arity@py_function_impl_base@objects@python@boost@@UBEIXZ) referenced in function $L65603 I went through the manual and could not find any hints on this, please help! Thanks, Qun

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(no subject)
by thilina sepala dahanayake Aug. 14, 2006

Aug. 14, 2006

fuck you man don't send me any mail again you are very very fool man

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boost.python newbie hassles
by Willi Richert Aug. 11, 2006

Aug. 11, 2006

Hi, As I am exploring whether I can let my students use it in our robotics group I like it more and more. However, there are some little problems for newbies: 1. the web doc is out of date. http://www.cs.brown.edu/people/jwicks/boost/libs/python/doc/tutorial/doc/ht… e.g. is very different from the doc in the tar.bz2 on sourceforge. A simple copy of the tar version to the web would be enough I think and save lots of trials. 2. boost.python projects have to be located in the boost directory tree, other than printed at the tutorial docs - as far as I have tried. If I move the tutorial greet example to another directory and update path-global in Jamrules I always get: wr@[ikarus]:~/workspace/Boost.Python/src> bjam Failed to find the project root for directory '.'. Did not find a project-root.jam file there or in any of its parent directories. Please consult the documentation at 'http://www.boost.org'. I'm using ubuntur 6.06. There I have installed boost-build libboost-python1.33.1 libboost-python-dev bjam In order to get the tutorial compiled I have to use the sf.net downloaded version. The above mentioned packages do not suffice. Shouldn't they? My version of bjam is Boost.Jam Version 3.1.11. OS=LINUX Regards, wr

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weird runtime error I'm getting with PyRun_SimpleFile()
by Blake Skinner Aug. 11, 2006

Aug. 11, 2006

Here's my C++ code, I'm building with VS 2005, under multi-threaded: #include <Python/python.h> #include <iostream> #include <cstdio> using namespace std; int main(int argc, char **argv) { Py_Initialize(); PyObject *main_module = PyImport_AddModule("__main__"); PyObject *main_dict = PyModule_GetDict(main_module); FILE *f = fopen("test.py", "r"); PyRun_SimpleFile(f, "test.py"); if (PyDict_GetItemString(main_dict, "num") == NULL) cout << "No" << endl; else cout << "Yes" << endl; Py_Finalize(); return 0; } When I run it, I get an error: Unhandled exception at 0x7c918fea in Embed_practice.exe: 0xC0000005: Access violation writing location 0x00000010 from a file called _file.c, the debugger calls attention to this method specificially: /*** * _lock_file - Lock a FILE * *Purpose: * Assert the lock for a stdio-level file * *Entry: * pf = __piob[] entry (pointer to a FILE or _FILEX) * *Exit: * *Exceptions: * *******************************************************************************/ void __cdecl _lock_file ( FILE *pf ) { /* * The way the FILE (pointed to by pf) is locked depends on whether * it is part of _iob[] or not */ if ( (pf >= _iob) && (pf <= (&_iob[_IOB_ENTRIES-1])) ) /* * FILE lies in _iob[] so the lock lies in _locktable[]. */ _lock( _STREAM_LOCKS + (int)(pf - _iob) ); else /* * Not part of _iob[]. Therefore, *pf is a _FILEX and the * lock field of the struct is an initialized critical * section. */ EnterCriticalSection( &(((_FILEX *)pf)->lock) ); } Any help solving this would be appreciated.

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can't build boost.python under msys/windows
by Jorge Vargas Aug. 11, 2006

Aug. 11, 2006

hi Could someone stop what I'm doing wrong? $ echo $PATH .:/usr/local/bin:/mingw/bin:/bin:/c/WINDOWS/system32:/c/WINDOWS:/c/WINDOWS/System32/Wbem:/c/Program Files/Subversion/bin:/c/Python24:/c/Python24/Scripts $ bjam "-sTOOLS=mgw" stage $ bjam "-sTOOLS=mingw" stage both commands fail doing a lot of lookups for vc-7_1 and the .Net framework (I have those install) CALL "C:\Program Files\Microsoft Visual Studio .NET 2003\VC7\bin\VCVARS32.BAT" >nul ...skipped <@boost!libs!python!build\libboost_python.lib\vc-7_1\debug\threading-multi>libboost_python.CMD for lack of <@boost!libs!python!build\libboost_python.lib\vc-7_1\debug\threading-multi> numeric.obj... ------ so I take them out of the path $ echo $PATH .:/usr/local/bin:/mingw/bin:/bin:/c/Python24:/c/Python24/Scripts $ bjam "-sTOOLS=mgw" stage and it fails to do anything $ bjam "-sTOOLS=mgw" stage ...found 944 targets... ...updating 121 targets... vc-C++ ..\..\..\bin\boost\libs\python\build\boost_python.dll\vc-7_1\debug\threading-multi\numeric.obj spawn: No such file or directory so basically bjam is ignoring the TOOLS flag I have to say I downloaded the binary for windows ( boost-jam-3.1.13-1-ntx86.zip) and all boostJam related links seems to be broken http://www.boost.org/doc/html/jam/building.html http://www.boost.org/tools/jam/index.html what I'm actually trying to do is porting this https://develop.participatoryculture.org/projects/democracy/wiki/WindowsBui… to compile with free tools so at the moment what I need is a replacement for boost_python-vc71-mt-1_33.dll that works with mingw does anyone distributes this as binary? thanks for the help.

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problem with iterator and non-destructible container
by James Pelletier Aug. 10, 2006

Aug. 10, 2006

I'm having trouble wrapping a container object that has a private destructor. As far as I can tell, the object has all of the necessary data to be used with the boost::python::iterator object, but when I try to compile I get an error message saying that the container's destructor is private. Why would the iterator want to destroy my container? Am I missing something? I'm using gcc-3.4 on solaris 10 on intel and boost-1.32. I couldn't find any differences in header files between boost 1.32 and 1.33 in this area. I've whittled it down to a small example below that gives me the same error message. The code compiles cleanly if I take out the .def("__iter__"...) line. ------- #include <vector> #include <boost/python.hpp> using namespace boost::python; class Y { Y() {} ~Y() {} Y( Y const & ); Y & operator=( Y const & ); std::vector<int> v_; public: typedef std::vector<int>::const_iterator const_iterator; const_iterator begin() const { return v_.begin(); } const_iterator end() const { return v_.end(); } }; BOOST_PYTHON_MODULE(boostpy) { class_<Y, boost::noncopyable>("Y", no_init) .def( "__iter__", iterator<Y const>() ) ; } ------ test.C: In static member function `static void boost::python::detail::value_destroyer< false>::execute(const volatile T*) [with T = Y]': /opt/app/g++lib6/boost-1.32/include/boost-1_32/boost/python/detail/destroy.hpp:90: instantiated from `void boost::python::detail::destroy_referent_impl(void*, T&(*)()) [with T = const Y]' /opt/app/g++lib6/boost-1.32/include/boost-1_32/boost/python/detail/destroy.hpp:101: instantiated from `void boost::python::detail::destroy_referent(void*, T (*)()) [with T = const Y&]' /opt/app/g++lib6/boost-1.32/include/boost-1_32/boost/python/converter/rvalue_from_python_data.hpp:135: instantiated from `boost::python::converter::rvalue_from_python_data<T>::~rvalue_from_python_data() [with T = const Y&]' /opt/app/g++lib6/boost-1.32/include/boost-1_32/boost/preprocessor/iteration/detail/local.hpp:34: instantiated from `PyObject* boost::python::detail::caller_arity<1u>::impl<F, Policies, Sig>::operator()(PyObject*, PyObject*) [with F = boost::python::objects::detail::py_iter_<const Y, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >, boost::_bi::protected_bind_t<boost::_bi::bind_t<__gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > (*)(const Y&), boost::_bi::list1<boost::arg<1> > > >, boost::_bi::protected_bind_t<boost::_bi::bind_t<__gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > (*)(const Y&), boost::_bi::list1<boost::arg<1> > > >, boost::python::return_value_policy<boost::python::return_by_value, boost::python::default_call_policies> >, Policies = boost::python::default_call_policies, Sig = boost::mpl::vector2<boost::python::objects::iterator_range<boost::python::return_value_policy<boost::python::return_by_value, boost::python::default_call_policies>, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > >, boost::python::back_reference<const Y&> >]' /opt/app/g++lib6/boost-1.32/include/boost-1_32/boost/python/object/py_function.hpp:38: instantiated from `PyObject* boost::python::objects::caller_py_function_impl<Caller>::operator()(PyObject*, PyObject*) [with Caller = boost::python::detail::caller<boost::python::objects::detail::py_iter_<const Y, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >, boost::_bi::protected_bind_t<boost::_bi::bind_t<__gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > (*)(const Y&), boost::_bi::list1<boost::arg<1> > > >, boost::_bi::protected_bind_t<boost::_bi::bind_t<__gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > (*)(const Y&), boost::_bi::list1<boost::arg<1> > > >, boost::python::return_value_policy<boost::python::return_by_value, boost::python::default_call_policies> >, boost::python::default_call_policies, boost::mpl::vector2<boost::python::objects::iterator_range<boost::python::return_value_policy<boost::python::return_by_value, boost::python::default_call_policies>, __gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > >, boost::python::back_reference<const Y&> > >]' test.C:37: instantiated from here test.C:10: error: `Y::~Y()' is private /opt/app/g++lib6/boost-1.32/include/boost-1_32/boost/python/detail/destroy.hpp:33: error: within this context

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C++ and Python variables referencing the same location
by tcickovs＠nd.edu Aug. 10, 2006

Aug. 10, 2006

Hello, I have been working on something for the past few days and have not been able to find much online help on it. Conceptually, what I want to do is very simple: I would like to declare a C++ variable, then use the Python/C API (or some other available utility) to define a Python variable, and then somehow get the two to reference the same memory location so that when I modify one, the other changes. So, for example, in my C++ file if I have this: object main_module(( handle<>(borrowed(PyImport_AddModule("__main__"))))); int y = 2; // y = 2 main_module.attr("x") = y; // x = 2, y = 2 main_module.attr("x") = 3; // x = 3, y = 2 (does not change) y = 4; // x = 3 (does not change), y = 4 Modifications to x and y happen independently because one is on the C++ runtime stack and the other is on the Python interpreter's heap. I'd like it to be if I modify x, then y changes; and vice-versa. Now, I saw in the Python/C API there was a way to modify information in the Python interpreter heap from C++: int* y = PyMem_New(int, 1); *y = 4; // Changes data in the heap However, I need to somehow get x to reference the location in the heap that I just allocated. Is there a way? Or is there a completely alternative solution that I can use? I feel like someone must have done this before, but cannot find much documentation. Appreciate any help at all. -Trevor

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Calling list.__len__() from C++ causes crash with >= 100 elements
by Geoffrey French Aug. 10, 2006

Aug. 10, 2006

Hi, I am currently running Python 2.4.3 and Boost 1.33.1-5 on Fedora Core 5. I have prepared some test code which seems to cause a seg fault when C++ code attempts to get the length of a list which has 100 or more elements. Valgrind seems to report it as an attempt to dereference a NULL pointer. An application that I have written (http://gsculpt.sf.net) displays the same behavior when compiled for Fedora Core 5, and Windows. Here is the code for a C++ module to demonstrate this: ======================== boostpythonbug.cpp ======================== #include <iostream> #include <boost/python.hpp> using namespace boost::python; void printListLength(boost::python::object elements) { boost::python::extract<int> lenExtract( elements.attr( "__len__" )() ); if ( lenExtract.check() ) { int numElements = lenExtract; std::cout << numElements << " elements" << std::endl; } } void printValue(boost::python::object obj) { boost::python::extract<int> vExtract( obj.attr( "value" )() ); if ( vExtract.check() ) { int v = vExtract; std::cout << "value = " << v << std::endl; } } BOOST_PYTHON_MODULE(ListLength) { def( "printListLength", &printListLength ); def( "printValue", &printValue ); } ======================== boostpythonbug.cpp ======================== To compile: $ c++ boostpythonbug.cpp --shared -o ListLength.so -lpython2.4-lboost_python -I/usr/include/python2.4 The python module below tests this module: ======================== boostpythonbug.py ======================== from ListLength import * class Test (object): def __init__(self, x): self.x = x def value(self): return self.x def __len__(self): return self.x printValue( Test( 5 ) ) printValue( Test( 99 ) ) printValue( Test( 100 ) ) printValue( Test( 101 ) ) printListLength( Test( 5 ) ) printListLength( Test( 99 ) ) printListLength( Test( 100 ) ) printListLength( Test( 101 ) ) printListLength( [] ) printListLength( [ 0 ] ) printListLength( range( 0, 5 ) ) printListLength( range( 0, 99 ) ) printListLength( range( 0, 100 ) ) ======================== boostpythonbug.py ======================== Here is the output: $ python boostpythonbug.py value = 5 value = 99 value = 100 value = 101 5 elements 99 elements 100 elements 101 elements 0 elements 1 elements 5 elements 99 elements Segmentation fault (core dumped) Getting integer values from a generic function call works fine, as demonstrated by printValue(), and printListLength() invoked on a 'Test' object. It only seems to affect lists. Defining printListLength as: void printListLength(boost::python::object elements) OR void printListLength(boost::python::list elements) does not prevent the seg-faulting. The second definition means you can only pass lists though, i.e. the cases where a 'Test' object is passed will not work. Is this a boost::python bug, or have I screwed up some how? Thank you for your time. Regards Geoffrey French

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boost python liking problems
by Eduardo Picado Aug. 9, 2006

Aug. 9, 2006

Hi, I'm trying to use Boost Python to wrap a 3rd party library. I have the headers, DLLs and a .lib file. When I try to compile my .cpp files I receive linkage errors: ------------- Creating library bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.lib and object bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.exp TASRNlSmlResult.obj : error LNK2001: unresolved external symbol "public: char const * __thiscall TASRNlSmlResult::str(void)const " (?str@TASRNlSmlResult@@QBEPBDXZ) …....... "link" /nologo /INCREMENTAL:NO /DEBUG /DLL /subsystem:console /out:"bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.pyd" /IMPLIB:"bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.lib " /LIBPATH:"c:\python22\libs" /LIBPATH:"bin\boost\libs\python\build\boost_python.dll\msvc\debug\threading-multi" /LIBPATH:"C:\PROGRA~1\MICROS~4\VC98\lib" "boost_python.lib" @"bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.CMD" ...failed vc-Link bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.pyd bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.lib... ...failed updating 1 target... --------------- I'm using bjam with canonical options. I guess I'm not correcting specifying where is the .lib file. How can I do this? Any ideas? Thanks, Eduardo Picado

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