Jan 14, 2026 · Jan 14, 2026
diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
                    _, dump_1, _ = assert_python_ok(*args, PYTHONHASHSEED="1")
                    self.assertEqual(dump_0, dump_1)

    def test_unmarshallable(self):
        # Check no crash after encountering unmarshallable objects.
        # See https://github.com/python/cpython/issues/106287.
        fset = frozenset([int])
        code = compile("a = 1", "<string>", "exec")
        code = code.replace(co_consts=(1, fset, None))
        cases = (('tuple', (fset,)),
                 ('list', [fset]),
                 ('set', fset),
                 ('dict key', {fset: 'x'}),
                 ('dict value', {'x': fset}),
                 ('dict key & value', {fset: fset}),
                 ('slice', slice(fset, fset)),
                 ('code', code))
        for name, arg in cases:
            with self.subTest(name, arg=arg):
                with self.assertRaisesRegex(ValueError, "unmarshallable object"):
                    marshal.dumps((arg, memoryview(b'')))


 LARGE_SIZE = 2**31
 pointer_size = 8 if sys.maxsize > 0xFFFFFFFF else 4

diff --git a/Misc/NEWS.d/next/Library/2025-04-19-17-34-11.gh-issue-132715.XXl47F.rst b/Misc/NEWS.d/next/Library/2025-04-19-17-34-11.gh-issue-132715.XXl47F.rst
 Skip writing objects during marshalling once a failure has occurred.
diff --git a/Python/marshal.c b/Python/marshal.c
 {
    char flag = '\0';

    if (p->error != WFERR_OK) {
        return;
    }

    p->depth++;

    if (p->depth > MAX_MARSHAL_STACK_DEPTH) {
Original file line number	Diff line number	Diff line change
Expand Up		@@ -406,6 +406,26 @@ def test_deterministic_sets(self):
		_, dump_1, _ = assert_python_ok(*args, PYTHONHASHSEED="1")
		self.assertEqual(dump_0, dump_1)

		def test_unmarshallable(self):
		# Check no crash after encountering unmarshallable objects.
		# See https://github.com/python/cpython/issues/106287.
		fset = frozenset([int])
		code = compile("a = 1", "<string>", "exec")
		code = code.replace(co_consts=(1, fset, None))
		cases = (('tuple', (fset,)),
		('list', [fset]),
		('set', fset),
		('dict key', {fset: 'x'}),
		('dict value', {'x': fset}),
		('dict key & value', {fset: fset}),
		('slice', slice(fset, fset)),
		('code', code))
		for name, arg in cases:
		with self.subTest(name, arg=arg):
		with self.assertRaisesRegex(ValueError, "unmarshallable object"):
		marshal.dumps((arg, memoryview(b'')))


		LARGE_SIZE = 2**31
		pointer_size = 8 if sys.maxsize > 0xFFFFFFFF else 4

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Skip writing objects during marshalling once a failure has occurred.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -362,6 +362,10 @@ w_object(PyObject v, WFILE p)
		{
		char flag = '\0';

		if (p->error != WFERR_OK) {
		return;
		}

		p->depth++;

		if (p->depth > MAX_MARSHAL_STACK_DEPTH) {
Expand Down