[C++-sig] Boost python extract on Mac OS Mavericks - seg fault

[Stefan Seefeld]

On 08/28/2014 06:19 PM, Brian Bruggeman wrote:
> Hi all,
>
> I am having trouble with a really simple example, and I am hoping
> someone on this list can help me.
>
> I have created a github repo for code in question:
>
> git clone git at github.com:brianbruggeman/boost_python_hello_world.git
>
> I have also created a stack overflow question:
>
> http://stackoverflow.com/q/25533329/631199
>
> The basic problem is as follows:
>
> Currently, I am able to compile cleanly, but when executing the code,
> I receive a segmentation fault. I've narrowed the seg-fault down to
> the line which actually uses boost::python::extract.

As a first step I suggest wrapping the code in a try-block, to catch
Python exceptions. You may also try extract::check() to verify whether
the object can in fact be converted to the specified type. (In your
version a conversion failure would result in an exception.)
I would also rewrite the code to use more of the Boost.Python API
(import, exec, etc.)

All that being said, the code compiles and runs fine for me (Fedora 20),
and I don't see anything wrong.

Regards,
Stefan





>
> Code:
>
> #include <boost/python.hpp>
> #include <iostream>
>
> namespace bp = boost::python;
>
> // Embedding python
> int main(int argc, char** argv) {
> int data = 0;
> Py_Initialize();
> PyRun_SimpleString("data = 1");
> bp::object
> module(bp::handle<>(bp::borrowed(PyImport_AddModule("__main__"))));
> bp::object dictionary = module.attr("__dict__");
> bp::object data_obj = dictionary["data"];
> // Error: The following line has the segmentation fault...
> data = bp::extract<int>(data_obj);
> std::cout << "data = " << data << std::endl;
> Py_Finalize();
> return 0;
> }
>
> CMakeLists.txt:
>
> project(hello)
> cmake_minimum_required(VERSION 2.8)
>
> FIND_PACKAGE(PythonInterp)
> FIND_PACKAGE(PythonLibs)
> FIND_PACKAGE(Boost COMPONENTS python)
>
> include_directories(${PYTHON_INCLUDE_DIRS} ${Boost_INCLUD_DIRS})
> link_directories(${PYTHON_LIBRARY_DIRS} ${Boost_LIBRARY_DIRS})
>
> add_executable(hello say_hello.cpp)
> target_link_libraries(hello
> ${Boost_LIBRARIES}
> ${PYTHON_LIBRARIES})
>
> Also for completeness…
>
> I installed Python and Boost::Python using the following…
>
> brew install python
> brew install boost —with-python
>
> Thanks so much in advance!
>
> Brian
>
>
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