Mailman 3 June 2008 - Cplusplus-sig

CMake and getting starting with boost.python
by Braddock Gaskill Aug. 5, 2011

Aug. 5, 2011

Yesterday I became a boost.python user, after years of heavy SWIG usage. I would have started using boost.python years ago except for the bjam learning curve. I spent hours TRYING on multiple occasions, but got lost every time trying to get the page one example to build with bjam. Here is how to build the "greet" example with a four line CMake file: cat >>CMakeLists.txt <<EOF LINK_LIBRARIES(boost_python) INCLUDE_DIRECTORIES("/usr/include/python2.5") LINK_DIRECTORIES("/usr/lib/python2.5") # Not needed? ADD_LIBRARY(hello SHARED hello.cpp) EOF You WILL have to `mv libhello.so hello.so` after building. Works for me under Ubuntu Linux 6.10 after apt-get install cmake python2.5-dev boost-python-dev cmake make mv libhello.so hello.so ipython In [1]: import hello In [2]: hello.greet() Out[2]: 'hello, world' Boost.Python has been a joy to learn and use since I got past bjam. I had a moderately large API wrapped in just my first couple hours of learning (less time than I spent messing with bjam). Any additional advice for using CMake to build boost.python? Braddock Gaskill

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How to import a boost::python dll in windows?
by ichijoji Aug. 5, 2011

Aug. 5, 2011

I'm trying to port some research code that uses boost::python to expose a library to python to windows, but I'm having trouble importing the dll into python. I'm compiling using msvc 2005 and using python 2.5, but when I try to import the module I get this: Traceback (most recent call last): File "main.py", line 1, in <module> import object File "c:\code\sge\code\scripts\object.py", line 1, in <module> import sge ImportError: No module named sge My module is named sge and I'm compiling to sge.dll. Is there some obvious reason why python wouldn't be able to find my dll? When I compile on linux into an so this code works fine. -- View this message in context: http://www.nabble.com/How-to-import-a-boost%3A%3Apython-dll-in-windows--tf3… Sent from the Python - c++-sig mailing list archive at Nabble.com.

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Bug and patch for boost.python with enable_shared_from_this
by Chad Austin March 26, 2009

March 26, 2009

Hi all, A month ago or so we discovered a bug in Boost.Python that manifests when using enable_shared_from_this. Here is a test case that demonstrates the bug: #include <boost/python.hpp> #include <boost/enable_shared_from_this.hpp> using namespace boost; using namespace boost::python; class Test; typedef shared_ptr<Test> TestPtr; class Test : public enable_shared_from_this<Test> { public: static TestPtr construct() { return TestPtr(new Test); } void act() { TestPtr kungFuDeathGrip(shared_from_this()); } void take(TestPtr t) { } }; void Export_test() { class_<Test, TestPtr, noncopyable>("Test") .def("construct", &Test::construct) .staticmethod("construct") .def("act", &Test::act) .def("take", &Test::take) ; } And here is the Python: x = Test.construct() x.take(x) x.act() The bug (as I understand it) is that the shared_ptr_from_python converter creates a new shared_ptr for the Test instance to pass it into C++. This new shared_ptr has a nop deleter, except that it keeps the Python object alive as long as the new shared_ptr is alive. The problem here is that creating a shared_ptr to an object of type T when T is enable_shared_from_this<T> resets the weak pointer inside of enable_shared_from_this<T>. (See shared_ptr's constructors for the details of the implementation.) A fix that passes the test above and has worked for us is to change shared_ptr's constructor to accept a dont_enable_shared_from_this argument and pass that in from the shared_ptr_from_python converter. The patch is attached (against boost 1.33, but the bug didn't look fixed in 1.34 either). Cheers, Chad p.s. I have seen other people with this problem as well. Googling for bad_weak_ptr turns up several results.

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py++ with template member function of template class
by Soloman Jan. 16, 2009

Jan. 16, 2009

Hi, I have met a problem using py++ (pyplusplus) to generate code. First, let's see this code: //////////////////////////////////////////////////////////////////////////////////// // template member function class AFunc { public: template <typename T> T foo(const T& t) const { return t + 1; } }; // we can only fully specialize function template <> string AFunc::foo<string>(const string& t) const { return "string"; }; // the following code is used to generate the instance of template functions #ifdef PYTHONWRAP void AFuncInit() { AFunc a; cout << a.foo<int>(1) << endl; cout << a.foo<float>(1.5f) << endl; cout << a.foo<string>("hello") << endl; }; #endif I followed the instruction in py++ homepage->FAQ, and this works, a call to a.foo<int> will generate an instance of that template member function. But, then, I used template class, and it won't work any more: ///////////////////////////////////////////////////////////////////////// // test template member function in template class // THIS WON'T WORK!!!!!!!!!!!!! template <typename A> class BFunc { public: template <typename T> T foo(const T& t) const; }; template <typename A> template <typename T> T BFunc<A>::foo(const T& t) const { return t + 1; }; #ifdef PYTHONWRAP typedef BFunc<int> BFunc_Int; void BFuncInit() { BFunc_Int a; //mem_fun(&BFunc_Int::foo<int>); //void * p = (void *)(&BFunc<int>::template foo<int>); cout << a.foo<int>(2) << endl; cout << a.foo<float>(2.5) << endl; //cout << a.foo<string>("hello") << endl; }; #endif Look into the generated code, I saw: bp::class_< AFunc >( "AFunc" ) .def( "foo" , (::std::string ( ::AFunc::* )( ::std::string const & ) const)( &::AFunc::foo ) , ( bp::arg("t") ) ) .def( "foo" , (float ( ::AFunc::* )( float const & ) const)( &::AFunc::foo ) , ( bp::arg("t") ) ) .def( "foo" , (int ( ::AFunc::* )( int const & ) const)( &::AFunc::foo ) , ( bp::arg("t") ) ); bp::class_< BFunc< int > >( "BFunc_Int" ); obviously, a call to BFunc_Int::foo<int> hasn't create the template member function instance, can anybody help me? Regards, Xiang.

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Re: [C++-sig] Bug and patch for boost.python with enable_shared_from_this
by Ralf W. Grosse-Kunstleve Dec. 23, 2008

Dec. 23, 2008

No news that I'm aware of. I'd be happy to check in patches, but someone else has to take the lead in communicating with Peter, and updating the unit tests. Ralf ----- Original Message ---- From: Edson Tadeu <e.tadeu(a)gmail.com> To: Development of Python/C++ integration <c++-sig(a)python.org> Sent: Thursday, February 28, 2008 11:45:32 AM Subject: Re: [C++-sig] Bug and patch for boost.python with enable_shared_from_this Any news on this issue? Will this patch get into Boost 1.35? Thanks, Edson On Wed, Feb 13, 2008 at 5:27 PM, Ralf W. Grosse-Kunstleve <rwgk(a)yahoo.com> wrote: Hi Chad, Could you at least ask Peter Dimov if he thinks the dont_enable_shared_from_this patch could be generally useful? Maybe he's OK adding it, then it wouldn't be a big deal fixing Boost.Python, which would probably prevent a lot of confusion and lost time in the future. http://www.boost.org/people/peter_dimov.htm p-d-i-m-o-v-at-m-m-l-t-d-dot-n-e-t Ralf ----- Original Message ---- From: Chad Austin <chad(a)imvu.com> To: Development of Python/C++ integration <c++-sig(a)python.org> Sent: Monday, February 11, 2008 10:10:31 PM Subject: Re: [C++-sig] Bug and patch for boost.python with enable_shared_from_this There probably is a way to prevent boost.python from creating shared_ptrs with a null deleter like it does, but it would require far more knowledge than I have. :) I agree that it would be a better fix, though. On 2/11/08, Ralf W. Grosse-Kunstleve <rwgk(a)yahoo.com> wrote: > > > > Thanks for the patch! I'd love to check this in for you, but for the > change in shared_ptr.hpp you'll need Peter Dimov's approval, and the > shared_ptr documentation would have to be updated. Also, your reproducer > should be turned into a unit test (in boost/libs/python/test). > > Is there any chance that the shared_ptr patch could somehow be avoided? > > Ralf > > > > ----- Original Message ---- > From: Chad Austin <chad(a)imvu.com> > To: c++-sig(a)python.org > Sent: Sunday, February 10, 2008 5:14:45 PM > Subject: [C++-sig] Bug and patch for boost.python with enable_shared_from_this > > Hi all, > > A month ago or so we discovered a bug in Boost.Python that manifests when using enable_shared_from_this. Here is a test case that demonstrates the bug: > > ... -----Inline Attachment Follows----- _______________________________________________ C++-sig mailing list C++-sig(a)python.org http://mail.python.org/mailman/listinfo/c++-sig

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Base class defined in other header file not included in bp::bases<>
by Haridev, Meghana Sept. 14, 2008

Sept. 14, 2008

Hi Folks, I'm having some trouble generating boost-python wrapper code using pyplusplus for a derived class which has one of its base classes defined in another file. Simple scenario: mydir/ other.hpp: class baseB{ }; hierarchy.hpp: #include "other.hpp" class baseA{ }; class derivedC: public baseA, public baseB{ }; generate_code.py: import os from pyplusplus import module_builder mb = module_builder.module_builder_t( files=['hierarchy.hpp'] ) mb.build_code_creator( module_name='inherit' ) mb.code_creator.user_defined_directories.append( os.path.abspath('.') ) mb.write_module('boost_hierarchy.cpp') ------------------------------------------------------------------------ ------------------------------------------------- Generated code (boost_hierarchy.cpp) looks like this: // This file has been generated by pyplusplus. #include "boost/python.hpp" #include "hierarchy.hpp" namespace bp = boost::python; BOOST_PYTHON_MODULE(inherit){ bp::class_< baseA >( "baseA" ); bp::class_< derivedC, bp::bases< baseA > >( "derivedC" ); } How can I get pyplusplus to add 'baseB' to bp::bases<> for 'derivedC' class when 'baseB' class is defined in another file (present in the same directory or different directory)? When I move the definition of 'baseB' class to hierarchy.hpp, boost wrapper for 'derivedC' is correctly generated as: bp::class_< derivedC, bp::bases< baseA, baseB > >( "derivedC" ); Thanks, -Meghana.

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Set optimization level for build_ext ??
by Michael Wieher June 30, 2008

June 30, 2008

Hey, trying to use valgrind with some libraries generated via native python's extension capabilities (not boost) so, by default I see gcc -pthread -fno-strict-aliasing -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -D_GNU_SOURCE -fPIC -fPIC -I/usr/include/python2.4 .... (my files) I want -O0 not -O2 so valgrind can find line numbers more correctly... I tried using "extra_complie_args" but that appends -O0 to the same line, still has -O2 ... not sure if -O0 over-rides the -O2 from earlier in the invocation or if it is ignored in favor of -O2 it looks like gcc -pthread -fno-strict-aliasing -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -D_GNU_SOURCE -fPIC -fPIC -I/usr/include/python2.4 -c memrid.cpp -o build/temp.linux-i686-2.4/memrid.o -O0 can anyone help me to be sure that I'm using NO optimization when this is compiled (ie: how to turn it on/off?) thanks, -mike

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Boost.Python embedding fails on MacOS X
by Marco Biasini June 30, 2008

June 30, 2008

Hi! I posted this mail on the boost users mailing list and was then pointed to this mailing-list. I've got a problem when using boost.python on MacOS X. The program exits with TypeError: attribute name must be string This happens both in boost 1.34 and 1.35. I was however able to run attached snippet without problems with boost 1.33. Code: #include <boost/python.hpp> using namespace boost::python; class CppClass { public: int getNum() { return 7; } }; int main( int argc, char ** argv ) { try { Py_Initialize(); object main_module(( handle<>(borrowed(PyImport_AddModule("__main__"))))); object main_namespace = main_module.attr("__dict__"); main_namespace["CppClass"] = class_<CppClass>("CppClass") .def("getNum",&CppClass::getNum); handle<> ignored(( PyRun_String( "cpp = CppClass();print cpp.getNum() \n", Py_file_input, main_namespace.ptr(), main_namespace.ptr() ) )); } catch( error_already_set ) { PyErr_Print(); } } Specs, if it should matter: * MacOS 10.4.11 * Compiler gcc 4.0.1 (Apple, Inc.), Python 2.4 (MacPorts) Any suggestions/directions? Please let me know if you need additional information. Best, Marco

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Embedded Python
by Craig Slusher June 27, 2008

June 27, 2008

I am having trouble with the following code: PyObject *module = PyImport_ImportModule(modulename); if (module == NULL) { PyObject* et, *ev, *etr; PyErr_Fetch(&et, &ev, &etr); PyObject* traceback = PyImport_ImportModule("traceback"); PyObject* tb = PyObject_CallMethodObjArgs(traceback, PyString_FromString("format_exception"), et, ev, etr, NULL); char *message = PyString_AsString(PyObject_Str(tb)); ... ... } When this code executes, it gets into the "module == NULL" condition. However, when I try to get the exception that occurred, I get the value "<NULL>" copied into the "char* message" variable. Can anyone shed some light on what might cause this to happen? I thought that if I actually get into that NULL condition that an exception has occurred. -- Craig Slusher cslush(a)gmail.com

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Problem running the simple Boost Python example
by Matthew Kwiec June 25, 2008

June 25, 2008

I cannot seem to get a Boost.Python project to run in Python. I have compiled the project using bjam from boost_1_33_1 but I cannot seem to figure out how to run it in Python. Currently in my output folder (which is in bin/boost/libs/python/build/libboost_python.so/gcc/debug/shared-linkable-true/) I have a hello.so, hello.o and a hello.so.1.33.1. What commands do I use to open these files in python? I have tried using the import command but it doesn't work with these and I cannot find a suitable way to call these libraries in Python. I am using boost_1_33_1 because the folks at work here have Debian installed as the OS and they couldn't seem to get 1_34 or 1_35 to compile properly with it. Thanks

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