gh-106287: do not write objects after an unmarshalling error

Lib/test/test_marshal.py

@@ -413,6 +413,26 @@ 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
 

Misc/NEWS.d/next/Library/2025-04-19-17-34-11.gh-issue-132715.XXl47F.rst

@@ -0,0 +1 @@
+Skip writing objects during marshalling once a failure has occurred.

Python/marshal.c

@@ -432,6 +432,10 @@ w_object(PyObject *v, WFILE *p)
 {
  char flag = '\0'
 
+ if (p->error != WFERR_OK){
+ return;
+ }
+
  p->depth++;
 
  if (p->depth > MAX_MARSHAL_STACK_DEPTH){