gh-116303: Skip tests if C recursion limit is unavailable (GH-117368)

The test suite fetches the C recursion limit from the _testcapi
extension module. Test extension modules can be disabled using the
--disable-test-modules configure option.

Author: erlend-aasland

Lib/test/list_tests.py

@@ -6,7 +6,7 @@
 from functools import cmp_to_key
 
 from test import seq_tests
-from test.support import ALWAYS_EQ, NEVER_EQ, Py_C_RECURSION_LIMIT
+from test.support import ALWAYS_EQ, NEVER_EQ, get_c_recursion_limit
 
 
 class CommonTest(seq_tests.CommonTest):
@@ -61,7 +61,7 @@ def test_repr(self):
 
     def test_repr_deep(self):
         a = self.type2test([])
-        for i in range(Py_C_RECURSION_LIMIT + 1):
+        for i in range(get_c_recursion_limit() + 1):
             a = self.type2test([a])
         self.assertRaises(RecursionError, repr, a)
 

Lib/test/mapping_tests.py

@@ -1,7 +1,7 @@
 # tests common to dict and UserDict
 import unittest
 import collections
-from test.support import Py_C_RECURSION_LIMIT
+from test.support import get_c_recursion_limit
 
 
 class BasicTestMappingProtocol(unittest.TestCase):
@@ -624,7 +624,7 @@ def __repr__(self):
 
     def test_repr_deep(self):
         d = self._empty_mapping()
-        for i in range(Py_C_RECURSION_LIMIT + 1):
+        for i in range(get_c_recursion_limit() + 1):
             d0 = d
             d = self._empty_mapping()
             d[1] = d0

Lib/test/support/__init__.py

@@ -56,7 +56,7 @@
     "run_with_tz", "PGO", "missing_compiler_executable",
     "ALWAYS_EQ", "NEVER_EQ", "LARGEST", "SMALLEST",
     "LOOPBACK_TIMEOUT", "INTERNET_TIMEOUT", "SHORT_TIMEOUT", "LONG_TIMEOUT",
-    "Py_DEBUG", "EXCEEDS_RECURSION_LIMIT", "Py_C_RECURSION_LIMIT",
+    "Py_DEBUG", "exceeds_recursion_limit", "get_c_recursion_limit",
     "skip_on_s390x",
     "without_optimizer",
     ]
@@ -2490,22 +2490,18 @@ def adjust_int_max_str_digits(max_digits):
         sys.set_int_max_str_digits(current)
 
 
-def _get_c_recursion_limit():
+def get_c_recursion_limit():
     try:
         import _testcapi
         return _testcapi.Py_C_RECURSION_LIMIT
-    except (ImportError, AttributeError):
-        # Originally taken from Include/cpython/pystate.h .
-        if sys.platform == 'win32':
-            return 4000
-        else:
-            return 10000
+    except ImportError:
+        raise unittest.SkipTest('requires _testcapi')
+
 
-# The default C recursion limit.
-Py_C_RECURSION_LIMIT = _get_c_recursion_limit()
+def exceeds_recursion_limit():
+    """For recursion tests, easily exceeds default recursion limit."""
+    return get_c_recursion_limit() * 3
 
-#For recursion tests, easily exceeds default recursion limit
-EXCEEDS_RECURSION_LIMIT = Py_C_RECURSION_LIMIT * 3
 
 #Windows doesn't have os.uname() but it doesn't support s390x.
 skip_on_s390x = unittest.skipIf(hasattr(os, 'uname') and os.uname().machine == 's390x',

Lib/test/test_ast.py

@@ -1153,9 +1153,9 @@ def next(self):
 
     @support.cpython_only
     def test_ast_recursion_limit(self):
-        fail_depth = support.EXCEEDS_RECURSION_LIMIT
+        fail_depth = support.exceeds_recursion_limit()
         crash_depth = 100_000
-        success_depth = int(support.Py_C_RECURSION_LIMIT * 0.8)
+        success_depth = int(support.get_c_recursion_limit() * 0.8)
         if _testinternalcapi is not None:
             remaining = _testinternalcapi.get_c_recursion_remaining()
             success_depth = min(success_depth, remaining)

Lib/test/test_collections.py

@@ -542,7 +542,7 @@ def test_odd_sizes(self):
         self.assertEqual(Dot(1)._replace(d=999), (999,))
         self.assertEqual(Dot(1)._fields, ('d',))
 
-        n = support.EXCEEDS_RECURSION_LIMIT
+        n = support.exceeds_recursion_limit()
         names = list(set(''.join([choice(string.ascii_letters)
                                   for j in range(10)]) for i in range(n)))
         n = len(names)

Lib/test/test_compile.py

@@ -13,7 +13,7 @@
 import warnings
 from test import support
 from test.support import (script_helper, requires_debug_ranges,
-                          requires_specialization, Py_C_RECURSION_LIMIT)
+                          requires_specialization, get_c_recursion_limit)
 from test.support.bytecode_helper import instructions_with_positions
 from test.support.os_helper import FakePath
 
@@ -114,7 +114,7 @@ def __getitem__(self, key):
 
     @unittest.skipIf(support.is_wasi, "exhausts limited stack on WASI")
     def test_extended_arg(self):
-        repeat = int(Py_C_RECURSION_LIMIT * 0.9)
+        repeat = int(get_c_recursion_limit() * 0.9)
         longexpr = 'x = x or ' + '-x' * repeat
         g = {}
         code = textwrap.dedent('''
@@ -634,9 +634,10 @@ def test_yet_more_evil_still_undecodable(self):
     @unittest.skipIf(support.is_wasi, "exhausts limited stack on WASI")
     def test_compiler_recursion_limit(self):
         # Expected limit is Py_C_RECURSION_LIMIT
-        fail_depth = Py_C_RECURSION_LIMIT + 1
-        crash_depth = Py_C_RECURSION_LIMIT * 100
-        success_depth = int(Py_C_RECURSION_LIMIT * 0.8)
+        limit = get_c_recursion_limit()
+        fail_depth = limit + 1
+        crash_depth = limit * 100
+        success_depth = int(limit * 0.8)
 
         def check_limit(prefix, repeated, mode="single"):
             expect_ok = prefix + repeated * success_depth

Lib/test/test_dict.py

@@ -8,7 +8,7 @@
 import unittest
 import weakref
 from test import support
-from test.support import import_helper, Py_C_RECURSION_LIMIT
+from test.support import import_helper, get_c_recursion_limit
 
 
 class DictTest(unittest.TestCase):
@@ -596,7 +596,7 @@ def __repr__(self):
 
     def test_repr_deep(self):
         d = {}
-        for i in range(Py_C_RECURSION_LIMIT + 1):
+        for i in range(get_c_recursion_limit() + 1):
             d = {1: d}
         self.assertRaises(RecursionError, repr, d)
 

Lib/test/test_dictviews.py

@@ -2,7 +2,7 @@
 import copy
 import pickle
 import unittest
-from test.support import Py_C_RECURSION_LIMIT
+from test.support import get_c_recursion_limit
 
 class DictSetTest(unittest.TestCase):
 
@@ -279,7 +279,7 @@ def test_recursive_repr(self):
 
     def test_deeply_nested_repr(self):
         d = {}
-        for i in range(Py_C_RECURSION_LIMIT//2 + 100):
+        for i in range(get_c_recursion_limit()//2 + 100):
             d = {42: d.values()}
         self.assertRaises(RecursionError, repr, d)
 

Lib/test/test_exception_group.py

@@ -1,7 +1,7 @@
 import collections.abc
 import types
 import unittest
-from test.support import Py_C_RECURSION_LIMIT
+from test.support import get_c_recursion_limit
 
 class TestExceptionGroupTypeHierarchy(unittest.TestCase):
     def test_exception_group_types(self):
@@ -460,7 +460,7 @@ def test_basics_split_by_predicate__match(self):
 class DeepRecursionInSplitAndSubgroup(unittest.TestCase):
     def make_deep_eg(self):
         e = TypeError(1)
-        for i in range(Py_C_RECURSION_LIMIT + 1):
+        for i in range(get_c_recursion_limit() + 1):
             e = ExceptionGroup('eg', [e])
         return e
 

Lib/test/test_exceptions.py

@@ -1424,7 +1424,7 @@ def gen():
             next(generator)
             recursionlimit = sys.getrecursionlimit()
             try:
-                recurse(support.EXCEEDS_RECURSION_LIMIT)
+                recurse(support.exceeds_recursion_limit())
             finally:
                 sys.setrecursionlimit(recursionlimit)
                 print('Done.')