gh-143460: Skip infinite recusion tests for infinite stack size (#143606)

Avoid tests being killed due to OOM on Linux if a system is configured with
'ulimit -s unlimited' by skipping tests relying on infinite recursion.

While unclear if Python should support 'ulimit -s unlimited', we should at
least try to avoid failing a PGO build running tests due to an unlimited
stack size being set.

Signed-off-by: Jan André Reuter <j.reuter@fz-juelich.de>

Author: Thyre

Lib/test/pickletester.py

@@ -2438,6 +2438,7 @@ def test_reduce_None(self):
         with self.assertRaises(TypeError):
             self.dumps(c)
 
+    @support.skip_if_unlimited_stack_size
     @no_tracing
     def test_bad_getattr(self):
         # Issue #3514: crash when there is an infinite loop in __getattr__

Lib/test/support/__init__.py

@@ -45,6 +45,7 @@
     "check__all__", "skip_if_buggy_ucrt_strfptime",
     "check_disallow_instantiation", "check_sanitizer", "skip_if_sanitizer",
     "requires_limited_api", "requires_specialization", "thread_unsafe",
+    "skip_if_unlimited_stack_size",
     # sys
     "MS_WINDOWS", "is_jython", "is_android", "is_emscripten", "is_wasi",
     "is_apple_mobile", "check_impl_detail", "unix_shell", "setswitchinterval",
@@ -1771,6 +1772,25 @@ def skip_if_pgo_task(test):
     return test if ok else unittest.skip(msg)(test)
 
 
+def skip_if_unlimited_stack_size(test):
+    """Skip decorator for tests not run when an unlimited stack size is configured.
+
+    Tests using support.infinite_recursion([...]) may otherwise run into
+    an infinite loop, running until the memory on the system is filled and
+    crashing due to OOM.
+
+    See https://github.com/python/cpython/issues/143460.
+    """
+    if is_wasi or os.name == "nt":
+        return test
+
+    import resource
+    curlim, maxlim = resource.getrlimit(resource.RLIMIT_STACK)
+    unlimited_stack_size_cond = curlim == maxlim and curlim in (-1, 0xFFFF_FFFF_FFFF_FFFF)
+    reason = "Not run due to unlimited stack size"
+    return unittest.skipIf(unlimited_stack_size_cond, reason)(test)
+
+
 def detect_api_mismatch(ref_api, other_api, *, ignore=()):
     """Returns the set of items in ref_api not in other_api, except for a
     defined list of items to be ignored in this check.

Lib/test/test_ast/test_ast.py

@@ -25,7 +25,7 @@
 
 from test import support
 from test.support import os_helper
-from test.support import skip_emscripten_stack_overflow, skip_wasi_stack_overflow
+from test.support import skip_emscripten_stack_overflow, skip_wasi_stack_overflow, skip_if_unlimited_stack_size
 from test.support.ast_helper import ASTTestMixin
 from test.support.import_helper import ensure_lazy_imports
 from test.test_ast.utils import to_tuple
@@ -989,6 +989,7 @@ def next(self):
         enum._test_simple_enum(_Precedence, _ast_unparse._Precedence)
 
     @support.cpython_only
+    @skip_if_unlimited_stack_size
     @skip_wasi_stack_overflow()
     @skip_emscripten_stack_overflow()
     def test_ast_recursion_limit(self):
@@ -1127,6 +1128,7 @@ def test_pickling(self):
                     ast2 = pickle.loads(pickle.dumps(tree, protocol))
                     self.assertEqual(to_tuple(ast2), to_tuple(tree))
 
+    @skip_if_unlimited_stack_size
     def test_copy_with_parents(self):
         # gh-120108
         code = """
@@ -1974,6 +1976,7 @@ def test_level_as_none(self):
         exec(code, ns)
         self.assertIn('sleep', ns)
 
+    @skip_if_unlimited_stack_size
     @skip_emscripten_stack_overflow()
     def test_recursion_direct(self):
         e = ast.UnaryOp(op=ast.Not(), lineno=0, col_offset=0, operand=ast.Constant(1))
@@ -1982,6 +1985,7 @@ def test_recursion_direct(self):
             with support.infinite_recursion():
                 compile(ast.Expression(e), "<test>", "eval")
 
+    @skip_if_unlimited_stack_size
     @skip_emscripten_stack_overflow()
     def test_recursion_indirect(self):
         e = ast.UnaryOp(op=ast.Not(), lineno=0, col_offset=0, operand=ast.Constant(1))

Lib/test/test_functools.py

@@ -438,6 +438,7 @@ def test_setstate_subclasses(self):
         self.assertIs(type(r[0]), tuple)
 
     @support.skip_if_sanitizer("thread sanitizer crashes in __tsan::FuncEntry", thread=True)
+    @support.skip_if_unlimited_stack_size
     @support.skip_emscripten_stack_overflow()
     def test_recursive_pickle(self):
         with replaced_module('functools', self.module):
@@ -2139,6 +2140,7 @@ def orig(a: int) -> nonexistent: ...
     @support.skip_on_s390x
     @unittest.skipIf(support.is_wasi, "WASI has limited C stack")
     @support.skip_if_sanitizer("requires deep stack", ub=True, thread=True)
+    @support.skip_if_unlimited_stack_size
     @support.skip_emscripten_stack_overflow()
     def test_lru_recursion(self):
 

Lib/test/test_isinstance.py

@@ -317,6 +317,7 @@ def __bases__(self):
             self.assertRaises(RecursionError, issubclass, int, X())
             self.assertRaises(RecursionError, isinstance, 1, X())
 
+    @support.skip_if_unlimited_stack_size
     @support.skip_emscripten_stack_overflow()
     @support.skip_wasi_stack_overflow()
     def test_infinite_recursion_via_bases_tuple(self):
@@ -328,6 +329,7 @@ def __getattr__(self, attr):
             with self.assertRaises(RecursionError):
                 issubclass(Failure(), int)
 
+    @support.skip_if_unlimited_stack_size
     @support.skip_emscripten_stack_overflow()
     @support.skip_wasi_stack_overflow()
     def test_infinite_cycle_in_bases(self):

Lib/test/test_json/test_recursion.py

@@ -68,6 +68,7 @@ def default(self, o):
             self.fail("didn't raise ValueError on default recursion")
 
 
+    @support.skip_if_unlimited_stack_size
     @support.skip_emscripten_stack_overflow()
     @support.skip_wasi_stack_overflow()
     def test_highly_nested_objects_decoding(self):
@@ -84,6 +85,7 @@ def test_highly_nested_objects_decoding(self):
             with support.infinite_recursion():
                 self.loads('[' * very_deep + '1' + ']' * very_deep)
 
+    @support.skip_if_unlimited_stack_size
     @support.skip_wasi_stack_overflow()
     @support.skip_emscripten_stack_overflow()
     @support.requires_resource('cpu')
@@ -99,6 +101,7 @@ def test_highly_nested_objects_encoding(self):
             with support.infinite_recursion(5000):
                 self.dumps(d)
 
+    @support.skip_if_unlimited_stack_size
     @support.skip_emscripten_stack_overflow()
     @support.skip_wasi_stack_overflow()
     def test_endless_recursion(self):

Lib/test/test_support.py

@@ -672,6 +672,7 @@ def test_recursive(depth, limit):
         """)
         script_helper.assert_python_ok("-c", code)
 
+    @support.skip_if_unlimited_stack_size
     def test_recursion(self):
         # Test infinite_recursion() and get_recursion_available() functions.
         def recursive_function(depth):

Lib/test/test_tomllib/test_misc.py

@@ -93,6 +93,7 @@ def test_deepcopy(self):
         }
         self.assertEqual(obj_copy, expected_obj)
 
+    @support.skip_if_unlimited_stack_size
     def test_inline_array_recursion_limit(self):
         with support.infinite_recursion(max_depth=100):
             available = support.get_recursion_available()
@@ -104,6 +105,7 @@ def test_inline_array_recursion_limit(self):
                 recursive_array_toml = "arr = " + nest_count * "[" + nest_count * "]"
                 tomllib.loads(recursive_array_toml)
 
+    @support.skip_if_unlimited_stack_size
     def test_inline_table_recursion_limit(self):
         with support.infinite_recursion(max_depth=100):
             available = support.get_recursion_available()

Misc/NEWS.d/next/Tests/2026-01-09-13-52-10.gh-issue-143460._nW2jt.rst

@@ -0,0 +1 @@
+Skip tests relying on infinite recusion if stack size is unlimited.