How to use shared_ptr in extern C when use python to call the so file?

I want to use C++ to make an so file on Linux,and use python to call the library.I use shared_ptr in extern C declare,compile success but get some error when call the library use python. I create some cpp files,like these: Calculator.h:

#ifndef HELLO_WORLD_CALCULATOR_H
#define HELLO_WORLD_CALCULATOR_H
class Calculator {
public:
    double add(double first, double second);
};
#endif

Calculator.cpp:

#include "Calculator.h"
double Calculator::add(double first, double second) {
    return first + second;
}

main.cpp:

#include <iostream>
#include <tr1/memory>
#include "Calculator.h"

using namespace std;

double devide1(double first, double second){
    shared_ptr<Calculator>calculater(new Calculator());
    return calculater->devide(first, second);
}

extern "C"
{
    double devide(double f, double s){
        return devide1(f,s);
    }
}

And I compile the file use this command: g++ main.cpp -fPIC -shared -o test.so -std=c++11 My python file test.py:

# coding=utf-8

import ctypes
from ctypes import *

if __name__ == "__main__":
    lib = ctypes.CDLL("./test.so")
    lib.devide.argstype = [c_double, c_double]
    lib.devide.restype = c_double
    print lib.devide(c_double(12), c_double(36))

And I run the program use python test.py in terminal.Then I got the error:

Traceback (most recent call last):
  File "test.py", line 9, in <module>
    lib = ctypes.CDLL("./test.so")
  File "/usr/lib/python2.7/ctypes/__init__.py", line 365, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: ./test.so: undefined symbol: _ZN10Calculator6devideEdd

How to fix the bug?