Compile C to shared library and load it using ffi

ffilib.py

#!/usr/bin/env python
"""
Quickly open an dylib connection. Helpful for testing and exploring.
"""

import os, sys
import glob2
# recursive glob, which is builtin function in python3
import subprocess
from cffi import FFI


def ffilib(libname):
    """
    open FFI object with dylib
    """
    headers = glob2.glob('**' + libname + '.h*')
    sources = glob2.glob('**' + libname + '.c*')

    if len(headers) != 1:
        print 'ERROR: could not find header for ' + libname
        sys.exit(1)
    if len(headers) != 1:
        print 'ERROR: could not find source for ' + libname
        sys.exit(1)

    header = headers[0]
    source = sources[0]

    ffi = FFI()
    ffi.cdef(subprocess.Popen(['cc', '-E', header],
                              stdout=subprocess.PIPE).communicate()[0])
    # dirty hack, ffi.verify() report error on osx
    # try compile dylib every time before open it
    dylib = libname + '.dylib'
    subprocess.call(['cc', '-dynamiclib', '-o', dylib, source])

    return ffi, ffi.dlopen(dylib)

def test_ffilib():
    ffi, lib = ffilib('hello')
    assert lib.num_int == 7
    assert lib.num_double == 0
    assert list(lib.array) == [1, 2, 3]
    assert lib.chr == "a"
    assert ffi.string(lib.string) == "CIVIC"
    assert lib.nul == ffi.NULL

hello.c

#include <stdio.h>
#include "hello.h"

hello.h

int num_int = 7;
double num_double = 0;
int array[3] = {1, 2, 3};
char chr = 'a';
char string[] = "CIVIC";
int *nul = NULL;