From 7359052467d5a7fdc013929df0f157c7277ebcfd Mon Sep 17 00:00:00 2001
From: "Michael J. Schultz" <mjschultz@gmail.com>
Date: Sat, 19 Apr 2014 13:24:09 -0500
Subject: [PATCH] Only build extensions against known good releases

---
 README.rst |  3 +++
 setup.py   | 17 ++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/README.rst b/README.rst
index a0026e0..e19a7ad 100644
--- a/README.rst
+++ b/README.rst
@@ -23,6 +23,9 @@ Or with the standard Python distutils incantation: ::
 	python setup.py build
 	python setup.py install
 
+The C extension will be built for supported python versions. If you do not
+want the C extension, set the environment variable ``RADIX_NO_EXT=1``.
+
 Tests are in the ``tests/`` directory and can be run with
 ``python setup.py test``.
 
diff --git a/setup.py b/setup.py
index 51146e5..4c8aa09 100755
--- a/setup.py
+++ b/setup.py
@@ -2,12 +2,19 @@
 
 import codecs
 import re
+import sys
+import os
 
 from setuptools import setup, find_packages, Extension
 from os.path import abspath, dirname, join
 
 here = abspath(dirname(__file__))
 
+# determine the python version
+IS_PYPY = hasattr(sys, 'pypy_version_info')
+IS_PY3K = (sys.version_info.major == 3)
+RADIX_NO_EXT = os.environ.get('RADIX_NO_EXT', False)
+
 
 # Read the version number from a source file.
 def find_version(*file_paths):
@@ -28,8 +35,12 @@ def find_version(*file_paths):
 with codecs.open(join(here, 'README.rst'), encoding='utf-8') as f:
     README = f.read()
 
-sources = ['radix/_radix.c', 'radix/_radix/radix.c']
-radix = Extension('radix._radix', sources=sources)
+# introduce some extra setup_args if Python 2.x
+extra_kwargs = {}
+if not IS_PYPY and not IS_PY3K and not RADIX_NO_EXT:
+    sources = ['radix/_radix.c', 'radix/_radix/radix.c']
+    radix = Extension('radix._radix', sources=sources)
+    extra_kwargs['ext_modules'] = [radix]
 
 
 setup(
@@ -53,6 +64,6 @@ def find_version(*file_paths):
     ],
     setup_requires=['nose', 'coverage'],
     packages=find_packages(exclude=['tests', 'tests.*']),
-    ext_modules=[radix],
     test_suite='nose.collector',
+    **extra_kwargs
 )