Mailman 3 October 2012 - Cplusplus-sig

boost::python embedding error - runtime - Mac OS X - 1.38
by Igor Karpov Oct. 1, 2014

Oct. 1, 2014

Hi, I am trying to run the following program: #include <iostream> #include <Python.h> #include <boost/python.hpp> using namespace boost::python; using namespace std; int main(int argc, char** argv) { { // Using Python/C Py_Initialize(); PyObject* main_module = PyImport_ImportModule("__main__"); PyObject* globals = PyEval_GetGlobals(); PyObject* locals = PyEval_GetLocals(); PyRun_SimpleString("print 'Hello World, from Python/C!'\n"); Py_Finalize(); } { // Using boost::python Py_Initialize(); object main_module = import("__main__"); object main_namespace = main_module.attr("__dict__"); try { object ignored = exec("print 'Hello World, from boost::python!'\n", main_namespace); Py_Finalize(); } catch (error_already_set const& e) { PyErr_Print(); return 1; } } return 0; } on Linux (both x86 and x86_64), with Ubuntu's default version of Boost (1.34.1) installed, I am able to do so as expected: $ ./embed Hello World, from Python/C! Hello World, from boost::python! on Mac OS X, I get a runtime error: $ ./embed Hello World, from Python/C! Bus Error Running with gdb, this is the stack trace: Hello World, from Python/C! Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_PROTECTION_FAILURE at address: 0x00000000 0x00000000 in ?? () (gdb) where #0 0x00000000 in ?? () #1 0x00bb618f in PyEval_GetGlobals () #2 0x00bce0dd in PyImport_Import () #3 0x00bce2b0 in PyImport_ImportModule () #4 0x008127d4 in boost::python::import (name=@0xbffff4a8) at libs/python/src/import.cpp:20 #5 0x00004446 in main (argc=1, argv=0xbffff510) at embed.cc:22 For this Mac, boost version is latest (1.38) and python version is: Python 2.5.4 (r254:67917, Dec 23 2008, 14:57:27) [GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin Is this a bug? I attached the source and the cmake file I am using to build, for convenience. Thanks, --Igor.

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sendkeys method
by sam Sept. 30, 2013

Sept. 30, 2013

Hello, Is there away(method) in C/C++ programming that make the software think that someone pressed the OK button, similar to sendkeys in VBS (WshShell.SendKeys ("{Enter}")) Thank you, Sam

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Boost.Python C++ exception translation question
by Jeffrey Van Voorst Oct. 30, 2012

Oct. 30, 2012

Greetings, I have used a method mentioned on stackoverflow (http://stackoverflow.com/questions/6908976/generalized-exception-translatio…) for a generalized method to translate C++ exceptions to python exceptions. When debugging my code using gdb the frames seem to indicate that a C++ requires a call to all of the translation instances. Is this because of a Boost.Python implementation issue, my deriving all my python exceptions from PyExc_EnvironmentError (using PyErr_NewException), or possibly a misunderstanding I have about C++ and template function evaluations? My code for a generic approach is: template<class E> class GeneralizedTranslator{ public: GeneralizedTranslator(PyObject* py_exc): A_PyExc(py_exc) { bp::register_exception_translator<E>(*this); } GeneralizedTranslator(const GeneralizedTranslator &other) : A_PyExc(other.A_PyExc) { ; } void operator()(const E &my_error) const { std::stringstream ostr; ostr << boost::diagnostic_information(my_error); PyErr_SetString(A_PyExc, ostr.str().c_str()); } private: PyObject *A_PyExc;}; // Allow for a simple translation declaration, remove scope problem template <class ErrType> void translate_error(PyObject *E) { GeneralizedTranslator<ErrType> my_translator(E); } New exceptions are created by: PyObject *PyExc_Error_A = PyError_NewException("Exception_A", PyExc_EnvironmentError, NULL); The class is used as: BOOST_PYTHON_MODULE(_test) { // Here the exceptions (My_Exception_*) are derived from boost::exception and std::exception translate_error<My_Exception_A>(PyExc_Error_A); translate_error<My_Exception_B>(PyExc_Error_B); . . . } In gdb I see: . . . #52 0x00007fffeff04827 in boost::detail::function::function_obj_invoker2<boost::_bi::bind_t<bool, boost::python::detail::translate_exception<My_Exception_B, GeneralizedTranslator<My_Exception_B> >, boost::_bi::list3<boost::arg<1>, boost::arg<2>, boost::_bi::value<GeneralizedTranslator<My_Exception_B> > > >, bool, boost::python::detail::exception_handler const&, boost::function0<void> const&>::invoke(boost::detail::function::function_buffer&, boost::python::detail::exception_handler const&, boost::function0<void> const&) () from /path/to/_test.so #53 0x00007ffff38a9ef4 in boost::python::detail::exception_handler::operator()(boost::function0<void> const&) const () from /path/to/libboost_python.so #54 0x00007fffeff04977 in boost::detail::function::function_obj_invoker2<boost::_bi::bind_t<bool, boost::python::detail::translate_exception<My_Exception_A, GeneralizedTranslator<My_Exception_A> >, boost::_bi::list3<boost::arg<1>, boost::arg<2>, boost::_bi::value<GeneralizedTranslator<My_Exception_A> > > >, bool, boost::python::detail::exception_handler const&, boost::function0<void> const&>::invoke(boost::detail::function::function_buffer&, boost::python::detail::exception_handler c onst&, boost::function0<void> const&) () from /path/to/_test.so #55 0x00007ffff38a9cfa in boost::python::handle_exception_impl(boost::function0<void>) () from /path/to/libboost_python.so #56 0x00007ffff38983e8 in ?? () from /path/to/libboost_python.so #57 0x000000000041ef47 in PyObject_Call () #58 0x00000000004a72b8 in PyEval_EvalFrameEx () #59 0x00000000004a95c1 in PyEval_EvalCodeEx () #60 0x00000000004a7752 in PyEval_EvalFrameEx () . . . Thanks, Jeff Van Voorst

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[boost.python] Register a Python-callable with C++ code and call it from C++ code?
by Paul O. Seidon Oct. 28, 2012

Oct. 28, 2012

I want to register Python-callables with my VariableFloat-class (which is a subclass of a template-class Variable<double>) and call them if the variable's value changes. For this I added an instance of class EventEmitter, which should hold references to those callbacks. So, VariableFloat delegates to EventEmitter, when it comes to deal with callbacks (reg'ing and calling). template <class TYPE> class EventEmitterSync3 { public: <snip/> void operator()() // Call the handler { if (_p_tau4eh) (*_p_tau4eh)( *this); }; void register_tau4ehS( void (*callable)( EventEmitterSync3<TYPE>& )) // Register the handler { _p_tau4eh = callable; }; <snip/> private: void (*_p_tau4eh)( EventEmitterSync3<TYPE>& ) = NULL; // The handler }; The class VariableFloat (actually its base class _Variable<TYPE>) holds a member of type EventEmitterSync<TYPE> like so: private: EventEmitterSync3<TYPE> _tau4ee_on_change; and the wrapper definitions are void (VariableFloat::*register_tau4ehS)( void (*)( EventEmitterSync3<double>& )) = &VariableFloat::register_tau4ehS; and .def( "register_tau4ehS", register_tau4ehS) Compiling yields errors coming from boost being rather cryptic to me. But the last few lines say: /media/truecrypt13/D.X/Projects/DDG/tau4/src/cpp/src/tau4misc/main.cpp:43:1: required from here /usr/include/boost/python/converter/registered.hpp:86:7: error: no matching function for call to ?register_shared_ptr1(void (*) (EventEmitterSync3<double>&))? /usr/include/boost/python/converter/registered.hpp:86:7: note: candidate is: /usr/include/boost/python/converter/registered.hpp:77:3: note: template<class T> void boost::python::converter::detail::register_shared_ptr1(const volatile T*) /usr/include/boost/python/converter/registered.hpp:77:3: note: template argument deduction/substitution failed: /usr/include/boost/python/converter/registered.hpp:86:7: note: types ?const volatile T? and ?void(EventEmitterSync3<double>&)? have incompatible cv-qualifiers Seems I have to put "const volatile" somewhere? I found some dox, which could be relevant, here: http://www.boost.org/doc/libs/1_51_0/libs/python/doc/v2/callbacks.html But I am not sure how to apply that info to my problem. I tried to change all function pointers into objects, but that didn't work. Has anyone some sample code on storing pointers to Python functions and then calling them and is willing to share it? Paul

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[boost.python] Can't import a wrapped template class
by Paul O. Seidon Oct. 27, 2012

Oct. 27, 2012

Hi all, right now I'm doing my first stepps in wrapping C++ code by ude of Boost. So, there's a template<class TYPE> class _Variable with ctor, dtor, an inspector TYPE value() const and a mutator void value( const TYPE& value). The boost wrapper looks like this: #include <Python.h> #include <boost/python.hpp> using namespace boost::python; #include "./src/varbls.h" #include <string> using namespace std; typedef _Variable<double> VariableDouble; BOOST_PYTHON_MODULE(_varbls) { class_<VariableDouble>("VariableDouble") .def( init<>()) .def( init<const double&>()) ; } Nothing special so far. However, what I get upon import is this: ImportError: /usr/lib/python2.7/site-packages/tau4.DDG/tau4/tau4misc/varbls/cpp/boost/_varbls.so: undefined symbol: _ZN9_VariableIdEC1Ev The ctor is decl'ed as _Variable(); and ist's def'ed like so: template <typename TYPE> _Variable<TYPE>::_Variable() : _value( 0) { //ctor } To me, everything looks good, but obiously there's something wrong. What do I miss? Paul

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Re: [C++-sig] How to hangle a NULL pointer?
by Jeffrey Van Voorst Oct. 2, 2012

Oct. 2, 2012

You might want to use wrapper functions in C++ boost::python::object gender_getter(const FaceObject& obj) { if(obj.gender == NULL) return Py_None; else return obj.gender; } Note: its been a bit since I used Boost.Python heavily. The syntax could be incorrect, but I hope this gives you a general idea. --Jeff Van Voorst

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How to hangle a NULL pointer?
by Luiz Vitor Martinez Cardoso Oct. 2, 2012

Oct. 2, 2012

Dear, I've a simple C++ class containing the following members: quint32 mergeCount; quint64 timestamp; quint32 id; quint32 score; quint32 lastScore; quint32 uptime; qint32 * gender; float * age; float * ageDeviationDen; quint32 * happy; quint32 * sad; quint32 * surprised; quint32 * angry; All the members are initialized to 0 or NULL if it's a pointer. The problem is that I'm getting a "Segmentation Fault" message when I try to access the pointers members from Python. The code I'm using to map the attributes are: void export_FaceObject() > { > class_<FaceObject, boost::noncopyable>("FaceObject", init<>()) > .add_property("mergecount", &FaceObject::getMergeCount) > .add_property("id", &FaceObject::getId) > .add_property("timestamp", &FaceObject::getTimestamp) > .add_property("score", &FaceObject::getScore) > .add_property("lastscore", &FaceObject::getLastScore) > .add_property("uptime", &FaceObject::getUptime) > .add_property("gender", &FaceObject::getGender) > .add_property("age", &FaceObject::getAge) > .add_property("agedeviation", &FaceObject::getAgeDeviation) > .add_property("happy", &FaceObject::getHappy) > .add_property("sad", &FaceObject::getSad) > .add_property("surprised", &FaceObject::getSurprised) > .add_property("angry", &FaceObject::getAngry) > ; > } What can I do? I know that I need to use a CallPolicy but I already have tried several combinations without any success. Best regards, Luiz Vitor. -- Regards, Luiz Vitor Martinez Cardoso Celular: (11) 7351-7097 | Skype: grabberbr engineer student at maua.br <http://maua.br>intern marketing engineer at geindustrial.com.br entrepreneur at adboxnetwork.com "If you wanna be successful, you need total dedication, go for your last limit, give your best and love your love infinitely!" "The only limits are the ones you place upon yourself"

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No Python class registered and a simple Qt type. Why?
by Luiz Vitor Martinez Cardoso Oct. 1, 2012

Oct. 1, 2012

Dear, I'm trying to integrate a simple Qt/C++ and Python... but I'm getting "*TypeError: No Python class registered for C++ class QString*" error message and I can't realize why. I already have read dozen of posts on mailing lists and Google search results... but I can't figure out the solution in my brain. Could someone help me? I'm attaching all the relevante code I use. Read it from last to the beginning =] *Boost.Python converters* * * > #ifndef QTTOPYOBJECTS_H > #define QTTOPYOBJECTS_H > #include "faceobject.h" > #include <boost/python.hpp> > using namespace boost::python; > // C = QList<T> > template <class C> > struct QList_to_python_list > { > typedef typename C::value_type T; > typedef typename C::const_iterator iter; > static PyObject* convert(C const &list) > { > // the python list > boost::python::list pyList; > foreach (const T& item, list) { > pyList.append(item); > } > return incref(pyList.ptr()); > } > }; > // C = QList<T*> > template <class C> > struct QList_ptr_to_python_list > { > typedef typename C::value_type T; > typedef typename C::const_iterator iter; > static PyObject* convert(C const &list) > { > // the python list > boost::python::list pyList; > // we need to wrap the pointers into PyObjects > typename boost::python::reference_existing_object::apply<T*>::type > converter; > for (iter i = list.begin(); i != list.end(); ++i) { > PyObject *obj = converter(*i); > object real_obj = object(handle<>(obj)); > // append the PyObject > pyList.append(real_obj); > } > return incref(pyList.ptr()); > } > }; > template <class C> > struct QList_ptr_from_python_list > { > typedef typename C::value_type T; > QList_ptr_from_python_list() > { > converter::registry::push_back( &convertible, &construct, type_id<C>() > ); > } > static void* convertible(PyObject *obj_ptr) > { > //is this a tuple type? > if (PyTuple_Check(obj_ptr)) { > //check the tuple elements... - convert to a boost::tuple object > boost::python::tuple t( handle<>(borrowed(obj_ptr)) ); > //how many elements are there? > int n = PyTuple_Size(obj_ptr); > //can they all be converted to type 'T'? > for (int i=0; i<n; ++i) { > if (!boost::python::extract<T>(t[i]).check()) > return 0; > } > //the tuple is ok! > return obj_ptr; > } > //is this a list type? > else if (PyList_Check(obj_ptr)) { > //check that all of the list elements can be converted to the right > type > boost::python::list l( handle<>(borrowed(obj_ptr)) ); > //how many elements are there? > int n = PyList_Size(obj_ptr); > //can all of the elements be converted to type 'T'? > for (int i=0; i<n; ++i) { > if (!boost::python::extract<T>(l[i]).check()) > return 0; > } > //the list is ok! > return obj_ptr; > } > //could not recognise the type... > return 0; > } > static void construct(PyObject *obj_ptr, > converter::rvalue_from_python_stage1_data *data) > { > if (PyTuple_Check(obj_ptr)) { > //convert the PyObject to a boost::python::object > boost::python::tuple t( handle<>(borrowed(obj_ptr)) ); > //locate the storage space for the result > void* storage = > ((converter::rvalue_from_python_storage<C>*)data)->storage.bytes; > //create the T container > new (storage) C(); > C *container = static_cast<C*>(storage); > //add all of the elements from the tuple - get the number of > elements in the tuple > int n = PyTuple_Size(obj_ptr); > for (int i=0; i<n; ++i) > container->append( extract<T>(t[i])() ); > data->convertible = storage; > } > else if (PyList_Check(obj_ptr)) { > //convert the PyObject to a boost::python::object > boost::python::list l( handle<>(borrowed(obj_ptr)) ); > //locate the storage space for the result > void* storage = > ((converter::rvalue_from_python_storage<C>*)data)->storage.bytes; > //create the T container > new (storage) C(); > C *container = static_cast<C*>(storage); > //add all of the elements from the tuple - get the number of > elements in the tuple > int n = PyList_Size(obj_ptr); > for (int i=0; i<n; ++i) > container->append( extract<T>(l[i])() ); > data->convertible = storage; > } > } > }; > struct QString_to_python_str > { > // FIXME: handle this using boost::python::str > static PyObject* convert(QString const &str) > { > #if defined ( Py_UNICODE_WIDE ) > PyObject *obj = PyUnicode_FromUnicode( 0, str.length() ); > if (!obj) > throw_error_already_set(); > Py_UNICODE *pyu = PyUnicode_AS_UNICODE( obj ); > for (int i = 0; i < str.length(); ++i) > *pyu++ = (str.at(i)).unicode(); > return obj; > #else > return PyUnicode_FromWideChar( (const wchar_t*) str.unicode(), > str.length() ); > #endif > } > }; > struct QString_from_python_str > { > QString_from_python_str() > { > converter::registry::push_back( &convertible, &construct, > type_id<QString>() ); > } > static void* convertible(PyObject *obj_ptr) > { > if (PyUnicode_Check(obj_ptr)) > return obj_ptr; > if (PyString_Check(obj_ptr)) > return obj_ptr; > return 0; > } > static void construct(PyObject *obj_ptr, > converter::rvalue_from_python_stage1_data *data) > { > if (PyUnicode_Check(obj_ptr)) { > void *storage = ((converter::rvalue_from_python_storage<QString> *) > data)->storage.bytes; > PY_UNICODE_TYPE *ucode = PyUnicode_AS_UNICODE(obj_ptr); > int len = PyUnicode_GET_SIZE(obj_ptr); > #if defined(Py_UNICODE_WIDE) > QString* out = new(storage) QString; > for ( int i = 0; i < len; ++i ) > out->append( (uint)ucode[i] ); > #else > new(storage) QString( (const QChar *)ucode, len ); > #endif > data->convertible = storage; > } else if ( PyString_Check( obj_ptr ) ) { > const char *value = PyString_AsString(obj_ptr); > if(!value) > throw_error_already_set(); > void *storage = ((converter::rvalue_from_python_storage<QString> *) > data)->storage.bytes; > new(storage) QString(QByteArray(value, PyString_Size(obj_ptr))); > data->convertible = storage; > } > } > }; > template <class C> > struct QList_from_python_list > { > typedef typename C::value_type T; > QList_from_python_list() > { > converter::registry::push_back( &convertible, &construct, type_id<C>() > ); > } > static void* convertible(PyObject *obj_ptr) > { > //is this a tuple type? > if (PyTuple_Check(obj_ptr)) { > //check the tuple elements... - convert to a boost::tuple object > boost::python::tuple t( handle<>(borrowed(obj_ptr)) ); > //how many elements are there? > int n = PyTuple_Size(obj_ptr); > //can they all be converted to type 'T'? > for (int i=0; i<n; ++i) { > if (!boost::python::extract<T>(t[i]).check()) > return 0; > } > //the tuple is ok! > return obj_ptr; > } > //is this a list type? > else if (PyList_Check(obj_ptr)) { > //check that all of the list elements can be converted to the right > type > boost::python::list l( handle<>(borrowed(obj_ptr)) ); > //how many elements are there? > int n = PyList_Size(obj_ptr); > //can all of the elements be converted to type 'T'? > for (int i=0; i<n; ++i) { > if (!boost::python::extract<T>(l[i]).check()) > return 0; > } > //the list is ok! > return obj_ptr; > } > //could not recognise the type... > return 0; > } > static void construct(PyObject *obj_ptr, > converter::rvalue_from_python_stage1_data *data) > { > if (PyTuple_Check(obj_ptr)) { > //convert the PyObject to a boost::python::object > boost::python::tuple t( handle<>(borrowed(obj_ptr)) ); > //locate the storage space for the result > void* storage = > ((converter::rvalue_from_python_storage<C>*)data)->storage.bytes; > //create the T container > new (storage) C(); > C *container = static_cast<C*>(storage); > //add all of the elements from the tuple - get the number of > elements in the tuple > int n = PyTuple_Size(obj_ptr); > for (int i=0; i<n; ++i) > container->append( extract<T>(t[i])() ); > data->convertible = storage; > } > else if (PyList_Check(obj_ptr)) { > //convert the PyObject to a boost::python::object > boost::python::list l( handle<>(borrowed(obj_ptr)) ); > //locate the storage space for the result > void* storage = > ((converter::rvalue_from_python_storage<C>*)data)->storage.bytes; > //create the T container > new (storage) C(); > C *container = static_cast<C*>(storage); > //add all of the elements from the tuple - get the number of > elements in the tuple > int n = PyList_Size(obj_ptr); > for (int i=0; i<n; ++i) > container->append( extract<T>(l[i])() ); > data->convertible = storage; > } > } > }; > > void export_QList() > { > to_python_converter< QList<QString>, QList_ptr_to_python_list< > QList<QString> > >(); > QList_ptr_from_python_list< QList<QString> >(); > } void export_QString() > { > to_python_converter< QString, QString_to_python_str >(); > QString_from_python_str(); > } #endif // QTTOPYOBJECTS_H *C++* > class QListTest > { > public: > QList<QString> constantStringList() > { > QList<QString> list; > list.append(QString("test 1")); > list.append(QString("test 2")); > list.append(QString("test 3")); > return list; > } > const QList<QString>& stringList() const > { > return m_list; > } > void setStringList(QList<QString> list) > { > m_list = list; > } > private: > QList<QString> m_list; > }; > > BOOST_PYTHON_MODULE(libfaceparser) > { > export_QString(); > export_QList(); > class_<QListTest>("QListTest") > .def("constantStringList", &QListTest::constantStringList) > .def("stringList", &QListTest::stringList, > return_value_policy<return_by_value>()) > .def("setStringList", &QListTest::setStringList) > ; > } *Python* import libfaceparser > > fp = libfaceparser.QListTest() > print fp.constantStringList() *Python Console* > lmvc@debian:~/Projects/adbox_server/adbox_parser/software/output/debug$ > python faceparser.py > Traceback (most recent call last): > File "faceparser.py", line 7, in <module> > print fp.constantStringList() > TypeError: No Python class registered for C++ class QString Best regards, Luiz Vitor. -- Regards, Luiz Vitor Martinez Cardoso Celular: (11) 7351-7097 | Skype: grabberbr engineer student at maua.br <http://maua.br>intern marketing engineer at geindustrial.com.br entrepreneur at adboxnetwork.com "If you wanna be successful, you need total dedication, go for your last limit, give your best and love your love infinitely!" "The only limits are the ones you place upon yourself"

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