Mailman 3 September 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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Weird problem with opaque pointers and pointers by reference
by Giuseppe Corbelli Sept. 24, 2012

Sept. 24, 2012

Hi all I am facing an "interesting" problem. I have factory functions implemented in C++ that create opaque pointers. Such pointers are tossed around in python and finally freed in C++. The module is implemented using boost::python. Platform gcc 4.6.3/debian/boost 1.46, but also tried on msvc8/win7/boost 1.43 The opaque pointer refers to an IplImage, a C struct defined by OpenCV image processing library. I'm attaching a complete test case, however, in short: IplImage* CreateImage() { IplImage* img = cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1); std::cout << "Created " << img << std::endl; return img; } void ReleaseImage(IplImage*& img) { std::cout << "Release Image " << img << std::endl; ::cvReleaseImage(&img); } When I run: img = CameraConnect_Fake_Python.CreateImage() CameraConnect_Fake_Python.ReleaseImage(img) here's the output: Created 0x8e34970 Release Image 0x70 Segmentation fault For some reason that I don't grasp the reference-to-pointer is not passed around correctly. Still more interesting, if I try: struct OPAQUE {int unused;}; OPAQUE* factory() { return new OPAQUE(); } void destroyer(OPAQUE*& x) { delete (x); x = NULL; } img = CameraConnect_Fake_Python.FACTORY() CameraConnect_Fake_Python.DESTROYER(img) It runs correctly! Hope someone can help... -- Giuseppe Corbelli WASP Software Engineer, Copan Italia S.p.A Phone: +390303666318 Fax: +390302659932 E-mail: giuseppe.corbelli(a)copanitalia.com

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using debug python with boost build
by John Reid Sept. 18, 2012

Sept. 18, 2012

Hi, I'm setting up my environment on a fresh machine with boost 1.51 and I can't get my python debug builds to work. I've got this in my user-config.jam using python ; using python : : /home/john/local/Python-2.7.3-dbg/bin/python : : : <python-debugging>on ; I've built a python debug and installed it into /home/john/local/Python-2.7.3-dbg/. I've also tried with the Ubuntu python debug package. I've set <python-debugging>on in the project I'm building but I get these error messages: capture-output /home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test ====== BEGIN OUTPUT ====== /home/john/local/Python-2.7.3-dbg/bin/python: can't open file 'python': [Errno 2] No such file or directory EXIT STATUS: 2 ====== END OUTPUT ====== LD_LIBRARY_PATH="/home/john/Dev/Bio/bin/Bio/gcc-4.6/debug/python-debugging-on:/home/john/Dev/Bio/bin/Biopsy/gcc-4.6/debug/python-debugging-on:/home/john/src/bin:/home/john/src/boost/boost_1_51_0/bin.v2/libs/chrono/build/gcc-4.6/debug/python-debugging-on/threading-multi:/home/john/src/boost/boost_1_51_0/bin.v2/libs/date_time/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/filesystem/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/program_options/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/python/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/regex/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/serialization/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/system/build/gcc-4.6/debug/python-debugging-on:/home/john/src/boost/boost_1_51_0/bin.v2/libs/system/bui ld/gcc-4.6/debug/python-debugging-on/threading-multi:/home/john/src/boost/boost_1_51_0/bin.v2/libs/thread/build/gcc-4.6/debug/python-debugging-on/threading-multi:/home/john/src/lib:/home/john/src/lib32:/home/john/src/lib64:/tmp/xercesc/lib:$LD_LIBRARY_PATH" export LD_LIBRARY_PATH PYTHONPATH="/home/john/Dev/Bio/bin/Biopsy/gcc-4.6/debug/python-debugging-on" export PYTHONPATH "/home/john/local/Python-2.7.3-dbg/bin/python" "python" "python_test/test_build_svg.py" > "/home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test.output" 2>&1 status=$? echo >> "/home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test.output" echo EXIT STATUS: $status >> "/home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test.output" if test $status -eq 0 ; then cp "/home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test.output" "/home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test" fi verbose=0 if test $status -ne 0 ; then verbose=1 fi if test $verbose -eq 1 ; then echo ====== BEGIN OUTPUT ====== cat "/home/john/Dev/Bio/bin/Biopsy/build_svg_test.test/gcc-4.6/debug/python-debugging-on/build_svg_test.output" echo ====== END OUTPUT ====== fi exit $status Any ideas where I'm going wrong? Thanks, John.

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How to compile static library with -fPIC from boost.python
by simon zhang Sept. 7, 2012

Sept. 7, 2012

Hi all Default,libboostpython.a has be compiled without -fPIC.But I have to make a python extending and it is a dynamic library with -fPIC that link to static library. How to compile static library (libboostpython.a) with -fPIC from boost.python simon

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building 32 Bit and 64 Bit extensions on the same machine
by Ronny Herzog Sept. 5, 2012

Sept. 5, 2012

Dear all, I want to build 32 bit extensions and 64 bit extensions on my Windows 7 / 32 Bit with boost. After two days of checking google I am a bit frustrated. I am new to Boost and it is a bit like a jungle. Can anyone help on what I need to do to set up Boost in the right way and have a Jamroot which allows me to compile my Python extensions in 32 Bit and 64 Bit at the same time (with MSVC 2008). Thanks a lot, Ronny

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Re: [C++-sig] More inheritance problems
by Charly Bicker Sept. 5, 2012

Sept. 5, 2012

Dear Holger, thank you for your reply! > Why is that needed? > >>> t = testInheritance.Third(testInheritance.Derived()) > her in reality an instance of DerivedWrapper is created, and then > passed to C++. When you then do `t.get_base()` and instance of > DerivedWrapper will be returned (there is actually some "magic" going > on that boost python can associate your `boost::shared_ptr<Base>` > with > the PyObject that is a DerivedWrapper). Because that object is a > `DerivedWrapper` the `.name` calls DerivedWrapper::name. > > In your second example the object is create with the call `_base = > boost::shared_ptr<Base>(new Derived());`. This class is no subclass > of > `DerivedWrapper` nor `BaseWrapper`, so you can not call a member > function of the wrappers. That is why you get the error. I see. I was working under the assumption, that the boost python magic included the treatment of classes Derived as their DerivedWrapper. Unfortunately, this leads me to another problem. In my simple example, the problem is fixed by just adding another function definition. However, for various reasons, some of my wrappers do more than just handle the function overloading: they convert certain objects to and from python. The conversions in question cannot be done with the usual converter classes, due to the use of an external C++ library with python bindings which is somewhat special (and might warrant another mail at some point). Now, wrapping like this with the behavior you describe will of course have disadvantageous effects because the conversions will only be done if the object was instantiated from python. Is there a way around this? Can I convince boost python to treat (i.e. convert) all instances of Derived as DerivedWrapper? If the answer is no, then that would obviously mean that the wrappers must not contain more than code for overloading and I would have solve the problems with the converters some other way. Best regards, Karl

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More inheritance problems
by Charly Bicker Sept. 4, 2012

Sept. 4, 2012

Dear all, first of all thanks to Holger for pointing me to a workaround with the add_static_property problem! Unfortunately, I already ran into the next problem, which seems very weird to me: I have again my old friends Base and Derived, with the obvious inheritance (source file attached). Now, there is a third class, named "Third", which has as a data member a boost::shared_ptr<Base> which is initialized in the constructor. For this reason, the constructor takes such a pointer as an argument. Now, the point where stuff goes wrong is this: the argument to the constructor has as a default value a NULL-boost::shared_ptr<Base>. The behavior now works as expected if the argument is provided in python: >>> import testInheritance >>> t = testInheritance.Third(testInheritance.Derived()) >>> t.get_base().name() 'Derived' >>> However, this fails if one does not provide an argument: >>> t = testInheritance.Third() >>> t.get_base().name() Traceback (most recent call last): File "<stdin>", line 1, in <module> Boost.Python.ArgumentError: Python argument types in Derived.name(Derived) did not match C++ signature: name(DerivedWrapper {lvalue}) name(DerivedWrapper {lvalue}) >>> I cannot wrap my head around this, can anybody point me to what I am doing wrong? I would be very grateful! Best regards, Karl Bicker

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Inheriting static overloaded properties
by Charly Bicker Sept. 4, 2012

Sept. 4, 2012

Dear all, I am working in the following scenario: I have a class "Derived" which inherits from "Base" and wrappers for both. Both have their own static debug flag and getters and setters for it (see code at the end of the mail). I try to use ".add_static_property" to make the debug flags visible in python, however if I do this for both Base and Derived, I get: python -c "import testInheritance" Traceback (most recent call last): File "<string>", line 1, in <module> Boost.Python.ArgumentError: Python argument types in None.None(Boost.Python.StaticProperty) did not match C++ signature: None(bool) Already when trying to import the module. If I do not add the property for Derived, I can import the module but then using debug on the Derived set the debug for Base instead. What am I doing wrong? Is this a bug? Does anybody know a solution? Any help would be greatly appreciated! Best regards, Karl Bicker PS: I would also like to make you aware of a stackoverflow question of mine: http://stackoverflow.com/questions/12202763/boost-python-inheriting-from-wr… Code: ---------------------------------------------------------------------------- #include<boost/python.hpp> namespace bp = boost::python; struct Base { Base() { }; static bool debug() { return _debug; }; static void setDebug(const bool debug = true) { _debug = debug; }; private: static bool _debug; }; struct BaseWrapper : Base, bp::wrapper<Base> { BaseWrapper() : Base(), bp::wrapper<Base>() { }; BaseWrapper(const Base& base) : Base(base), bp::wrapper<Base>() { }; }; struct Derived : Base { Derived() : Base() { }; static bool debug() { return _debug; }; static void setDebug(const bool debug = true) { _debug = debug; }; private: static bool _debug; }; struct DerivedWrapper : Derived, bp::wrapper<Derived> { DerivedWrapper() : Derived(), bp::wrapper<Derived>() { }; DerivedWrapper(const Derived derived) : Derived(derived), bp::wrapper<Derived>() { }; }; bool Base::_debug = false; bool Derived::_debug = false; BOOST_PYTHON_MODULE(testInheritance){ bp::class_<BaseWrapper>("Base") .add_static_property("debug", &BaseWrapper::debug, &BaseWrapper::setDebug); bp::class_<DerivedWrapper, bp::bases<Base> >("Derived") .add_static_property("debug", &DerivedWrapper::debug, &DerivedWrapper::setDebug); }

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How to make a python function as callback of a c++ function
by simon zhang Sept. 3, 2012

Sept. 3, 2012

I have to make a python function as callback of a c++ function.How to do?Where can I find some examples?? I want to use boost.python. I want my code look something like this: In C++ : typedef void (*MyCallback_t) (CallbackInfo); > class MyClass > {... > void setcallback(MyCallback_t cb); > ... > } And to use it in python : import mylib class mypythonclass: def myCallback(mylib_CallbackInfo): .... def mywork(): t = mylib.MyClass() t.setcallback(self.myCallback)

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