Test _imp._set_lazy_attributes() at shutdown, add a comment and reword NEWS

Author: brittanyrey

Lib/test/test_lazy_import/__init__.py

@@ -2846,6 +2846,21 @@ def __del__(self, write=os.write, type=type, ns=ns):
         """)
         self.assertEqual(assert_python_ok("-c", code).out, b"module")
 
+    def test_set_lazy_attributes(self):
+        code = textwrap.dedent("""
+            import _imp, os, sys
+
+            class Canary:
+                def __del__(self, write=os.write,
+                            set_lazy=_imp._set_lazy_attributes):
+                    set_lazy(None, "mod")
+                    write(1, b"ok")
+
+            # Freed while sys.lazy_modules is being cleared.
+            sys.lazy_modules.add(Canary())
+        """)
+        self.assertEqual(assert_python_ok("-c", code).out, b"ok")
+
 
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2026-10-05-01-59-22.gh-issue-158820.3KLyOT.rst

@@ -1 +1,2 @@
-Fix a segfault triggered by declaring or resolving a lazy import within a finalizer during shutdown.
+Fix a crash when a :ref:`lazy import <lazy-imports>` is declared or resolved
+by a finalizer running during interpreter shutdown.

Python/import.c

@@ -4219,6 +4219,7 @@ register_lazy_on_parent(PyThreadState *tstate, PyObject *name, PyObject *source)
 {
     PyDictObject *pending =
         (PyDictObject *)LAZY_PENDING_SUBMODULES(tstate->interp);
+    // Finalizers can still run after finalize_modules() cleared the dict.
     if (pending == NULL) {
         return 0;
     }