gh-118846: Fix free-threading test failures when run sequentially (#118864)

The free-threaded build currently immortalizes some objects once the
first thread is started. This can lead to test failures depending on the
order in which tests are run. This PR addresses those failures by
suppressing immortalization or skipping the affected tests.

Author: colesbury

Lib/test/seq_tests.py

@@ -426,6 +426,7 @@ def test_pickle(self):
             self.assertEqual(lst2, lst)
             self.assertNotEqual(id(lst2), id(lst))
 
+    @support.suppress_immortalization()
     def test_free_after_iterating(self):
         support.check_free_after_iterating(self, iter, self.type2test)
         support.check_free_after_iterating(self, reversed, self.type2test)

Lib/test/test_capi/test_misc.py

@@ -26,7 +26,8 @@
 from test.support import threading_helper
 from test.support import warnings_helper
 from test.support import requires_limited_api
-from test.support import requires_gil_enabled, expected_failure_if_gil_disabled
+from test.support import suppress_immortalization
+from test.support import expected_failure_if_gil_disabled
 from test.support import Py_GIL_DISABLED
 from test.support.script_helper import assert_python_failure, assert_python_ok, run_python_until_end
 try:
@@ -481,6 +482,7 @@ def test_heap_ctype_doc_and_text_signature(self):
     def test_null_type_doc(self):
         self.assertEqual(_testcapi.NullTpDocType.__doc__, None)
 
+    @suppress_immortalization()
     def test_subclass_of_heap_gc_ctype_with_tpdealloc_decrefs_once(self):
         class HeapGcCTypeSubclass(_testcapi.HeapGcCType):
             def __init__(self):
@@ -498,6 +500,7 @@ def __init__(self):
         del subclass_instance
         self.assertEqual(type_refcnt - 1, sys.getrefcount(HeapGcCTypeSubclass))
 
+    @suppress_immortalization()
     def test_subclass_of_heap_gc_ctype_with_del_modifying_dunder_class_only_decrefs_once(self):
         class A(_testcapi.HeapGcCType):
             def __init__(self):

Lib/test/test_descr.py

@@ -5014,6 +5014,7 @@ def __new__(cls):
                 cls.lst = [2**i for i in range(10000)]
         X.descr
 
+    @support.suppress_immortalization()
     def test_remove_subclass(self):
         # bpo-46417: when the last subclass of a type is deleted,
         # remove_subclass() clears the internal dictionary of subclasses:

Lib/test/test_gc.py

@@ -3,7 +3,8 @@
 from test import support
 from test.support import (verbose, refcount_test,
                           cpython_only, requires_subprocess,
-                          requires_gil_enabled)
+                          requires_gil_enabled, suppress_immortalization,
+                          Py_GIL_DISABLED)
 from test.support.import_helper import import_module
 from test.support.os_helper import temp_dir, TESTFN, unlink
 from test.support.script_helper import assert_python_ok, make_script
@@ -109,6 +110,7 @@ def test_tuple(self):
         del l
         self.assertEqual(gc.collect(), 2)
 
+    @suppress_immortalization()
     def test_class(self):
         class A:
             pass
@@ -117,6 +119,7 @@ class A:
         del A
         self.assertNotEqual(gc.collect(), 0)
 
+    @suppress_immortalization()
     def test_newstyleclass(self):
         class A(object):
             pass
@@ -133,6 +136,7 @@ class A:
         del a
         self.assertNotEqual(gc.collect(), 0)
 
+    @suppress_immortalization()
     def test_newinstance(self):
         class A(object):
             pass
@@ -219,6 +223,7 @@ class B(object):
             self.fail("didn't find obj in garbage (finalizer)")
         gc.garbage.remove(obj)
 
+    @suppress_immortalization()
     def test_function(self):
         # Tricky: f -> d -> f, code should call d.clear() after the exec to
         # break the cycle.
@@ -561,6 +566,7 @@ def test_get_referents(self):
 
         self.assertEqual(gc.get_referents(1, 'a', 4j), [])
 
+    @suppress_immortalization()
     def test_is_tracked(self):
         # Atomic built-in types are not tracked, user-defined objects and
         # mutable containers are.
@@ -598,7 +604,9 @@ class UserFloatSlots(float):
         class UserIntSlots(int):
             __slots__ = ()
 
-        self.assertTrue(gc.is_tracked(gc))
+        if not Py_GIL_DISABLED:
+            # gh-117783: modules may be immortalized in free-threaded build
+            self.assertTrue(gc.is_tracked(gc))
         self.assertTrue(gc.is_tracked(UserClass))
         self.assertTrue(gc.is_tracked(UserClass()))
         self.assertTrue(gc.is_tracked(UserInt()))
@@ -1347,6 +1355,10 @@ def callback(ignored):
         junk = []
         i = 0
         detector = GC_Detector()
+        if Py_GIL_DISABLED:
+            # The free-threaded build doesn't have multiple generations, so
+            # just trigger a GC manually.
+            gc.collect()
         while not detector.gc_happened:
             i += 1
             if i > 10000:
@@ -1415,6 +1427,10 @@ def __del__(self):
         detector = GC_Detector()
         junk = []
         i = 0
+        if Py_GIL_DISABLED:
+            # The free-threaded build doesn't have multiple generations, so
+            # just trigger a GC manually.
+            gc.collect()
         while not detector.gc_happened:
             i += 1
             if i > 10000:

Lib/test/test_inspect/test_inspect.py

@@ -34,7 +34,7 @@
 except ImportError:
     ThreadPoolExecutor = None
 
-from test.support import cpython_only, import_helper
+from test.support import cpython_only, import_helper, suppress_immortalization
 from test.support import MISSING_C_DOCSTRINGS, ALWAYS_EQ
 from test.support.import_helper import DirsOnSysPath, ready_to_import
 from test.support.os_helper import TESTFN, temp_cwd
@@ -768,6 +768,7 @@ def test_getfile_builtin_function_or_method(self):
             inspect.getfile(list.append)
         self.assertIn('expected, got', str(e_append.exception))
 
+    @suppress_immortalization()
     def test_getfile_class_without_module(self):
         class CM(type):
             @property
@@ -2430,6 +2431,7 @@ def __getattribute__(self, attr):
 
         self.assertFalse(test.called)
 
+    @suppress_immortalization()
     def test_cache_does_not_cause_classes_to_persist(self):
         # regression test for gh-118013:
         # check that the internal _shadowed_dict cache does not cause

Lib/test/test_module/__init__.py

@@ -4,6 +4,7 @@
 import weakref
 from test.support import gc_collect
 from test.support import import_helper
+from test.support import suppress_immortalization
 from test.support.script_helper import assert_python_ok
 
 import sys
@@ -103,6 +104,7 @@ def f():
         gc_collect()
         self.assertEqual(f().__dict__["bar"], 4)
 
+    @suppress_immortalization()
     def test_clear_dict_in_ref_cycle(self):
         destroyed = []
         m = ModuleType("foo")
@@ -118,6 +120,7 @@ def __del__(self):
         gc_collect()
         self.assertEqual(destroyed, [1])
 
+    @suppress_immortalization()
     def test_weakref(self):
         m = ModuleType("foo")
         wr = weakref.ref(m)

Lib/test/test_trace.py

@@ -1,7 +1,7 @@
 import os
 from pickle import dump
 import sys
-from test.support import captured_stdout, requires_resource
+from test.support import captured_stdout, requires_resource, requires_gil_enabled
 from test.support.os_helper import (TESTFN, rmtree, unlink)
 from test.support.script_helper import assert_python_ok, assert_python_failure
 import textwrap
@@ -301,6 +301,7 @@ def test_loop_caller_importing(self):
 
     @unittest.skipIf(hasattr(sys, 'gettrace') and sys.gettrace(),
                      'pre-existing trace function throws off measurements')
+    @requires_gil_enabled("gh-117783: immortalization of types affects traced method names")
     def test_inst_method_calling(self):
         obj = TracedClass(20)
         self.tracer.runfunc(obj.inst_method_calling, 1)
@@ -334,6 +335,7 @@ def setUp(self):
 
     @unittest.skipIf(hasattr(sys, 'gettrace') and sys.gettrace(),
                      'pre-existing trace function throws off measurements')
+    @requires_gil_enabled("gh-117783: immortalization of types affects traced method names")
     def test_loop_caller_importing(self):
         self.tracer.runfunc(traced_func_importing_caller, 1)
 

Lib/test/test_zoneinfo/test_zoneinfo.py

@@ -17,7 +17,7 @@
 from datetime import date, datetime, time, timedelta, timezone
 from functools import cached_property
 
-from test.support import MISSING_C_DOCSTRINGS
+from test.support import MISSING_C_DOCSTRINGS, requires_gil_enabled
 from test.test_zoneinfo import _support as test_support
 from test.test_zoneinfo._support import OS_ENV_LOCK, TZPATH_TEST_LOCK, ZoneInfoTestBase
 from test.support.import_helper import import_module, CleanImport
@@ -1931,6 +1931,7 @@ def test_cache_location(self):
         self.assertFalse(hasattr(c_zoneinfo.ZoneInfo, "_weak_cache"))
         self.assertTrue(hasattr(py_zoneinfo.ZoneInfo, "_weak_cache"))
 
+    @requires_gil_enabled("gh-117783: types may be immortalized")
     def test_gc_tracked(self):
         import gc