Segmentation fault when using boost::numpy::ndarray

Question

I am getting what I think is a strange seg fault when I am trying to pass boost::numpy::ndarray as an argument:

#include <iostream>
#include <boost/python.hpp>
#include <boost/numpy.hpp>


void say_hello(boost::numpy::ndarray& my_array)
//void say_hello(int x) This works fine
{
  std::cout<<"Hello"<<std::endl;
}

BOOST_PYTHON_MODULE(hello_ext)
{
    using namespace boost::python;
    def("say_hello", say_hello);

}

I know the example is silly, but I should not be getting a seg fault there, and this is the smallest example I was able to reduce the problem to. Maybe I need to specify the ndarray type or number of dimensions, but I could not find any documentation on it. I was looking at this, but it didn't seem very helpful. My gut feeling is I am missing something simple, but I just don't see it.

When I run this:

In [1]: from hello_ext import *

In [2]: import numpy as np

In [3]: say_hello(np.array([3,4,5]))
Segmentation fault (core dumped)

My Makefile:

PYTHON_VERSION = 2.7
PYTHON_INCLUDE = /usr/include/python$(PYTHON_VERSION)


BOOST_INC = /usr/include
BOOST_LIB = /usr/lib

TARGET = hello_ext

$(TARGET).so: $(TARGET).o
    g++ -std=c++11 -shared -Wl,--export-dynamic $(TARGET).o -L$(BOOST_LIB) -lboost_python -lboost_numpy -L/usr/lib/python$(PYTHON_VERSION)/config -lpython$(PYTHON_VERSION) -o $(TARGET).so

$(TARGET).o: $(TARGET).cpp
    g++ -std=c++11 -I$(PYTHON_INCLUDE) -I$(BOOST_INC) -fPIC -c $(TARGET).cp

Akavall · Accepted Answer · 2014-07-13 18:11:25Z

11

I knew it was something simple. I needed to add these two lines:

Py_Initialize();
boost::numpy::initialize();

as explained : here seg fault results after any attempt to use boost::numpy::ndarray if the above lines are not ran.

Therefore: my file becomes:

#include <iostream>
#include <boost/python.hpp>
#include <boost/numpy.hpp>


void say_hello(boost::numpy::ndarray& my_array)
//void say_hello(int x) This works fine
{
  std::cout<<"Hello"<<std::endl;
}

BOOST_PYTHON_MODULE(hello_ext)
{
    using namespace boost::python;
    Py_Initialize();
    boost::numpy::initialize();
    def("say_hello", say_hello);
}

edited Jul 13, 2014 at 18:11

answered Jul 13, 2014 at 15:43

Akavall

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2 Comments

Walter Over a year ago

But in the linked example, the initialisation is done in a C++ main(). Here, we are in a python module.

Mehdi Over a year ago

Thank you very much!! This is the kind of cryptic segfault not even GDB can help with

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