First (uncontroversial) part of issue 9807.

* Expose the build flags to Python as sys.abiflags
* Shared library libpythonX.Y<abiflags>.so
* python-config --abiflags
* Make two distutils tests that failed with --enable-shared (even before this
  patch) succeed.
* Fix a few small style issues.

command/build_ext.py

@@ -754,9 +754,9 @@ class build_ext(Command):
         else:
             from distutils import sysconfig
             if sysconfig.get_config_var('Py_ENABLE_SHARED'):
-                template = "python%d.%d"
-                pythonlib = (template %
-                             (sys.hexversion >> 24, (sys.hexversion >> 16) & 0xff))
+                pythonlib = 'python{}.{}{}'.format(
+                    sys.hexversion >> 24, (sys.hexversion >> 16) & 0xff,
+                    sys.abiflags)
                 return ext.libraries + [pythonlib]
             else:
                 return ext.libraries

tests/test_build_ext.py

 import sys
 import os
-import tempfile
 import shutil
 from io import StringIO
 
-from distutils.core import Extension, Distribution
+from distutils.core import Distribution
 from distutils.command.build_ext import build_ext
 from distutils import sysconfig
 from distutils.tests.support import TempdirManager
 from distutils.tests.support import LoggingSilencer
 from distutils.extension import Extension
-from distutils.errors import (UnknownFileError, DistutilsSetupError,
-                              CompileError)
+from distutils.errors import (
+    CompileError, DistutilsSetupError, UnknownFileError)
 
 import unittest
 from test import support
@@ -42,6 +41,20 @@ class BuildExtTestCase(TempdirManager,
             from distutils.command import build_ext
             build_ext.USER_BASE = site.USER_BASE
 
+    def _fixup_command(self, cmd):
+        # When Python was build with --enable-shared, -L. is not good enough
+        # to find the libpython<blah>.so.  This is because regrtest runs it
+        # under a tempdir, not in the top level where the .so lives.  By the
+        # time we've gotten here, Python's already been chdir'd to the
+        # tempdir.
+        #
+        # To further add to the fun, we can't just add library_dirs to the
+        # Extension() instance because that doesn't get plumbed through to the
+        # final compiler command.
+        if not sys.platform.startswith('win'):
+            library_dir = sysconfig.get_config_var('srcdir')
+            cmd.library_dirs = [('.' if library_dir is None else library_dir)]
+
     def test_build_ext(self):
         global ALREADY_TESTED
         xx_c = os.path.join(self.tmp_dir, 'xxmodule.c')
@@ -49,6 +62,7 @@ class BuildExtTestCase(TempdirManager,
         dist = Distribution({'name': 'xx', 'ext_modules': [xx_ext]})
         dist.package_dir = self.tmp_dir
         cmd = build_ext(dist)
+        self._fixup_command(cmd)
         if os.name == "nt":
             # On Windows, we must build a debug version iff running
             # a debug build of Python
@@ -235,7 +249,8 @@ class BuildExtTestCase(TempdirManager,
         cmd.finalize_options()
 
         #'extensions' option must be a list of Extension instances
-        self.assertRaises(DistutilsSetupError, cmd.check_extensions_list, 'foo')
+        self.assertRaises(DistutilsSetupError,
+                          cmd.check_extensions_list, 'foo')
 
         # each element of 'ext_modules' option must be an
         # Extension instance or 2-tuple
@@ -302,6 +317,7 @@ class BuildExtTestCase(TempdirManager,
         dist = Distribution({'name': 'xx',
                              'ext_modules': [ext]})
         cmd = build_ext(dist)
+        self._fixup_command(cmd)
         cmd.ensure_finalized()
         self.assertEquals(len(cmd.get_outputs()), 1)