Mailman 3 November 2013 - 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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Wrapping Boost graph vertex/edge descriptors (void pointers) with Boost.Python
by Rocco Moretti Nov. 25, 2013

Nov. 25, 2013

Hello all, We have a C++ library that uses the Boost graph library, and has functions which return and take the boost graph vertex and edge descriptors. The issue I'm running into with using Boost.Python is that for the implementation of the graph that we've chose (the listS/listS one), the edge and vertex descriptors are internally implemented as void pointers. Not using void pointers isn't an option (the use of void pointers is a choice by Boost graph for the style of graph we're using, which has other considerations feeding into it). I don't really need to interact with the vertex and edge descriptors at all at the Python level, aside from passing them around and then back to other C++ level functions (and perhaps doing equality comparisons, but that's not strictly necessary). I certainly don't need to dereference them or type convert them. Even at the C++ level we never deal with them as actual void pointers, instead having them be typedefed, and using that consistent typedefed type as an opaque type. What would be the best way to have Boost.Python deal with these edge and vertex descriptors? I looked at opaque pointer policy stuff, but from what I can tell so far, that doesn't really work with void pointers. Thank You, -Rocco

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Error importing a python module in c++
by Tobias Opitz Nov. 2, 2013

Nov. 2, 2013

Hello mailinglist, I'm having trouble embedding python into c++. I use msvc-9.0, building 32-bit on a 64-architecture running win7pro. My Python version is 2.7.5. I have a python release and debug version (every file in C.\python27\libs exists with and without _d) I would like to embed a couple of python scripts into a c++-application. Therefore I first tried to use the standard Python C-API. The problem I encountered during this is the same as described here<http://wangqiang8511.com/2012/07/18/embedding-python-in-c-application/>. So I tried to use boost.python but this was neither successfully. I'm receiving a acces violation. Here is my example source code: #include <Python.h> // without this line the compiler criticizes a missing python27.lib - // but I'm trying to build a debug-variant... #include <iostream> #include <boost/python.hpp> int main() { std::cout << "Boost.Python Test" << std::endl; // Start Python interpreter Py_Initialize(); // Setup sys.path boost::python::object sys = boost::python::import("sys"); // => throws "0x00000000 in Python_C_API_Test.exe: 0xC0000005: Access violation." in boost/libs/python/src/import.cpp boost::python::list path = boost::python::extract<boost::python::list>(sys.attr("path")); std::cout << "Module loaded" << std::endl; return 0; } I have build boost.python a dozend times with different flags. ("D:\boost_1_53_0>b2 --build-dir="D:\boost_1_53_0\python" toolset=msvc-9.0 link=shared variant=debug --python-debugging python" and using the resulting "boost_python-vc90-mt-gd-1_53.lib" What could I have missed? Do you have any solutions or approachs for me? Thanks in advance.

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