gh-149676: fix: properly initialise frozendict hash value#149675
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KowalskiThomas wants to merge 3 commits into
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gh-149676: fix: properly initialise frozendict hash value#149675KowalskiThomas wants to merge 3 commits into
frozendict hash value#149675KowalskiThomas wants to merge 3 commits into
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KowalskiThomas
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frozendict hash valuefrozendict hash value
vstinner
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May 11, 2026
| if (result != NULL) { | ||
| /* ma_hash must be -1 (sentinel for "not computed") since PyObject_GC_New | ||
| does not zero-initialize memory and new_dict_impl does not touch ma_hash. */ | ||
| _PyFrozenDictObject_CAST(result)->ma_hash = -1; |
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Can you move this assignment to new_dict_impl()? Adding an int frozendict parameter.
| PyObject *result = new_dict_impl(mp, keys, values, used, free_values_on_failure); | ||
| if (result != NULL) { | ||
| /* ma_hash must be -1 (sentinel for "not computed") since PyObject_GC_New | ||
| does not zero-initialize memory and new_dict_impl does not touch ma_hash. */ |
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I don't think that this comment is useful.
| with self.assertRaisesRegex(TypeError, "unhashable type: 'list'"): | ||
| hash(fd) | ||
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| def test_hash_pipe_operator(self): |
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You should move this test to existing test_merge().
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| # gh-149676: frozendict created via | must have the same hash as one | ||
| # created directly with the same contents (ma_hash must be initialised | ||
| # to -1 so that the hash is computed on first call, not left as garbage) | ||
| a = frozendict({"a": 1}) | ||
| b = frozendict({"b": 2}) | ||
| c = frozendict({"a": 1, "b": 2}) | ||
| c_union = a | b | ||
| self.assertEqual(c, c_union) | ||
| self.assertEqual(hash(c), hash(c_union)) |
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The self.assertEqual(c, c_union) test is redundant with test_merge() tests. I suggest to simplify the test to:
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| # gh-149676: frozendict created via | must have the same hash as one | |
| # created directly with the same contents (ma_hash must be initialised | |
| # to -1 so that the hash is computed on first call, not left as garbage) | |
| a = frozendict({"a": 1}) | |
| b = frozendict({"b": 2}) | |
| c = frozendict({"a": 1, "b": 2}) | |
| c_union = a | b | |
| self.assertEqual(c, c_union) | |
| self.assertEqual(hash(c), hash(c_union)) | |
| # gh-149676: Test hash(frozendict | frozendict) | |
| a = frozendict({"a": 1}) | |
| b = frozendict({"b": 2}) | |
| self.assertEqual(hash(a | b), hash(frozendict({"a": 1, "b": 2}))) |
| @@ -0,0 +1 @@ | |||
| Fix :class:`frozendict` instances being created with an uninitialised hash value, which could cause incorrect hash lookups or crashes. | |||
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The issue cannot lead to a crash. I suggest:
Fix frozendict | frozendict hash.
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frozendict's hash is not initialised when created through pipe operator #149676