bpo-43795: Add a test for Stable ABI symbol availability using ctypes (GH-26354)

This is a cross-platform check that the symbols are actually
exported in the ABI, not e.g. hidden in a macro.

Caveat: PyModule_Create2 & PyModule_FromDefAndSpec2 are skipped.

These aren't exported on some of our buildbots. This is a bug
(bpo-44133). This test now makes sure all the others don't regress.

Tools/scripts/stable_abi.py

@@ -258,6 +258,44 @@ def gen_doc_annotations(manifest, args, outfile):
             'added': item.added,
             'ifdef_note': ifdef_note})
 
+@generator("ctypes_test", 'Lib/test/test_stable_abi_ctypes.py')
+def gen_ctypes_test(manifest, args, outfile):
+    """Generate/check the ctypes-based test for exported symbols"""
+    write = partial(print, file=outfile)
+    write(textwrap.dedent('''
+        # Generated by Tools/scripts/stable_abi.py
+
+        """Test that all symbols of the Stable ABI are accessible using ctypes
+        """
+
+        import unittest
+        from test.support.import_helper import import_module
+
+        ctypes_test = import_module('ctypes')
+
+        class TestStableABIAvailability(unittest.TestCase):
+            def test_available_symbols(self):
+                for symbol_name in SYMBOL_NAMES:
+                    with self.subTest(symbol_name):
+                        ctypes_test.pythonapi[symbol_name]
+
+        SYMBOL_NAMES = (
+    '''))
+    items = manifest.select(
+        {'function', 'data'},
+        include_abi_only=True,
+        ifdef=set())
+    for item in items:
+        if item.name in (
+                # Some symbols aren't exported on all platforms.
+                # This is a bug: https://bugs.python.org/issue44133
+                'PyModule_Create2', 'PyModule_FromDefAndSpec2',
+            ):
+            continue
+        write(f'    "{item.name}",')
+    write(")")
+
+
 def generate_or_check(manifest, args, path, func):
     """Generate/check a file with a single generator