use py_limited_api flag when available.

In setuptools>=26, Extension(..., py_limited_api=True) sets the .abi3.so
filename, readable by Python 3.2+.

2 files changed, 43 insertions, 1 deletions

diff --git a/cffi/setuptools_ext.py b/cffi/setuptools_ext.py
index 9c6436d..a579285 100644
--- a/cffi/setuptools_ext.py
+++ b/cffi/setuptools_ext.py
@@ -69,16 +69,33 @@ def add_cffi_module(dist, mod_spec):
     else:
         _add_c_module(dist, ffi, module_name, source, source_extension, kwds)
 
+def _set_py_limited_api(Extension, kwds):
+    """
+    Add py_limited_api to kwds if setuptools >= 26 is in use.
+    Do not alter the setting if it already exists.
+    Setuptools takes care of ignoring the flag on Python 2 and PyPy.
+    """
+    if Extension.__module__.startswith('setuptools.') and not 'py_limited_api' in kwds:
+        import setuptools
+        try:
+            setuptools_major_version = int(setuptools.__version__.partition('.')[0])
+            if setuptools_major_version >= 26:
+                kwds['py_limited_api'] = True
+        except ValueError:  # certain development versions of setuptools
+            pass
+    return kwds
 
 def _add_c_module(dist, ffi, module_name, source, source_extension, kwds):
     from distutils.core import Extension
-    from distutils.command.build_ext import build_ext
+    # We are a setuptools extension. Need this build_ext for py_limited_api.
+    from setuptools.command.build_ext import build_ext
     from distutils.dir_util import mkpath
     from distutils import log
     from cffi import recompiler
 
     allsources = ['$PLACEHOLDER']
     allsources.extend(kwds.pop('sources', []))
+    kwds = _set_py_limited_api(Extension, kwds)
     ext = Extension(name=module_name, sources=allsources, **kwds)
 
     def make_mod(tmpdir, pre_run=None):
diff --git a/testing/cffi0/test_zintegration.py b/testing/cffi0/test_zintegration.py
index 2736eb1..dcc4873 100644
--- a/testing/cffi0/test_zintegration.py
+++ b/testing/cffi0/test_zintegration.py
@@ -148,3 +148,28 @@ class TestZIntegration(object):
         p = snip_setuptools_verify2.C.getpwuid(0)
         assert snip_setuptools_verify2.ffi.string(p.pw_name) == b"root"
         ''')
+
+    def test_set_py_limited_api(self):
+        from cffi.setuptools_ext import _set_py_limited_api
+        try:
+            import setuptools
+            orig_version = setuptools.__version__
+            setuptools.__version__ = '26.0.0'
+            from setuptools import Extension
+
+            kwds = _set_py_limited_api(Extension, {})
+            assert kwds['py_limited_api'] == True
+
+            kwds = _set_py_limited_api(Extension.__base__, {})
+            assert not kwds
+
+            setuptools.__version__ = '25.0'
+            kwds = _set_py_limited_api(Extension, {})
+            assert not kwds
+
+            setuptools.__version__ = 'development'
+            kwds = _set_py_limited_api(Extension, {})
+            assert not kwds
+
+        finally:
+            setuptools.__version__ = orig_version