Merge pull request #718 from dholth/master

use abi3 extension if Extension().is_abi3

CHANGES.rst

@@ -44,6 +44,14 @@ v25.1.3
 * #714 and #704: Revert fix as it breaks other components
   downstream that can't handle unicode. See #709, #710,
   and #712.
+* Add Extension(py_limited_api=True). When set to a truthy value,
+  that extension gets a filename apropriate for code using Py_LIMITED_API.
+  When used correctly this allows a single compiled extension to work on
+  all future versions of CPython 3.
+  The py_limited_api argument only controls the filename. To be
+  compatible with multiple versions of Python 3, the C extension
+  will also need to set -DPy_LIMITED_API=... and be modified to use
+  only the functions in the limited API.
 
 v25.1.2
 -------

setuptools/command/build_ext.py

@@ -59,6 +59,14 @@ elif os.name != 'nt':
 
 if_dl = lambda s: s if have_rtld else ''
 
+def get_abi3_suffix():
+    """Return the file extension for an abi3-compliant Extension()"""
+    import imp
+    for suffix, _, _ in (s for s in imp.get_suffixes() if s[2] == imp.C_EXTENSION):
+        if '.abi3' in suffix:   # Unix
+            return suffix
+        elif suffix == '.pyd':  # Windows
+            return suffix
 
 class build_ext(_build_ext):
 
@@ -96,6 +104,13 @@ class build_ext(_build_ext):
         filename = _build_ext.get_ext_filename(self, fullname)
         if fullname in self.ext_map:
             ext = self.ext_map[fullname]
+            if (sys.version_info[0] != 2 
+                and getattr(ext, 'py_limited_api')
+                and get_abi3_suffix()):
+                from distutils.sysconfig import get_config_var
+                so_ext = get_config_var('SO')
+                filename = filename[:-len(so_ext)]
+                filename = filename + get_abi3_suffix()
             if isinstance(ext, Library):
                 fn, ext = os.path.splitext(filename)
                 return self.shlib_compiler.library_filename(fn, libtype)

setuptools/extension.py

@@ -36,6 +36,10 @@ have_pyrex = _have_cython
 class Extension(_Extension):
     """Extension that uses '.c' files in place of '.pyx' files"""
 
+    def __init__(self, name, sources, py_limited_api=False, **kw):
+        self.py_limited_api = py_limited_api
+        _Extension.__init__(self, name, sources, **kw)
+
     def _convert_pyx_sources_to_lang(self):
         """
         Replace sources with .pyx extensions to sources with the target

setuptools/tests/test_build_ext.py

+import sys
 import distutils.command.build_ext as orig
 
-from setuptools.command.build_ext import build_ext
+from distutils.sysconfig import get_config_var
+from setuptools.command.build_ext import build_ext, get_abi3_suffix
 from setuptools.dist import Distribution
-
+from setuptools.extension import Extension
 
 class TestBuildExt:
 
@@ -18,3 +20,24 @@ class TestBuildExt:
         res = cmd.get_ext_filename('foo')
         wanted = orig.build_ext.get_ext_filename(cmd, 'foo')
         assert res == wanted
+
+    def test_abi3_filename(self):
+        """
+        Filename needs to be loadable by several versions
+        of Python 3 if 'is_abi3' is truthy on Extension()
+        """
+        print(get_abi3_suffix())
+        
+        extension = Extension('spam.eggs', ['eggs.c'], py_limited_api=True)
+        dist = Distribution(dict(ext_modules=[extension]))
+        cmd = build_ext(dist)
+        cmd.finalize_options()
+        assert 'spam.eggs' in cmd.ext_map
+        res = cmd.get_ext_filename('spam.eggs')
+
+        if sys.version_info[0] == 2 or not get_abi3_suffix():
+            assert res.endswith(get_config_var('SO'))
+        elif sys.platform == 'win32':
+            assert res.endswith('eggs.pyd')
+        else:
+            assert 'abi3' in res
\ No newline at end of file