gh-132617: Fix dict.update() mutation check
#134815
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Use `ma_used` instead of `ma_keys->dk_nentries` for modification check so that we only check if the dictionary is modified, not if new keys are added to a different dictionary that shared the same keys object.
colesbury
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needs backport to 3.13
colesbury
changed the title
dict.update() mutation checkdict.update() mutation check
mpage
reviewed
May 28, 2025
methane
reviewed
May 28, 2025
| @@ -3858,7 +3858,7 @@ dict_dict_merge(PyInterpreterState *interp, PyDictObject *mp, PyDictObject *othe | |||
| } | |||
| } | |||
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| Py_ssize_t orig_size = other->ma_keys->dk_nentries; | |||
| Py_ssize_t orig_size = other->ma_used; | |||
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ma_used is too weak. It cannot detect del d["a"]; d["b"] = None.
For better check:
- For all table, check
other->ma_keysis not changed. - For combined table, check
other->ma_keys->dk_nentriesis not changed. - For split table, check
other->ma_values->sizeis not changed.
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It's the same condition we use in iterators and elsewhere. I don't think we should strengthen any of the checks. These are heuristic checks, they're not going to be perfect, but if we decide to do so, I think we should do that in a subsequent PR and not backport that change.
Lines 5169 to 5174 in 469a564
mpage
approved these changes
Jun 4, 2025
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Thanks @colesbury for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14. |
miss-islington
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Jun 16, 2025
Use `ma_used` instead of `ma_keys->dk_nentries` for modification check so that we only check if the dictionary is modified, not if new keys are added to a different dictionary that shared the same keys object. (cherry picked from commit d8994b0) Co-authored-by: Sam Gross <[email protected]>
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Sorry, @colesbury, I could not cleanly backport this to |
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GH-135581 is a backport of this pull request to the 3.14 branch. |
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GH-135582 is a backport of this pull request to the 3.13 branch. |
colesbury
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Jun 16, 2025
…134815) Use `ma_used` instead of `ma_keys->dk_nentries` for modification check so that we only check if the dictionary is modified, not if new keys are added to a different dictionary that shared the same keys object. (cherry picked from commit d8994b0) Co-authored-by: Sam Gross <[email protected]>
colesbury
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Jun 16, 2025
…135581) Use `ma_used` instead of `ma_keys->dk_nentries` for modification check so that we only check if the dictionary is modified, not if new keys are added to a different dictionary that shared the same keys object. (cherry picked from commit d8994b0) Co-authored-by: Sam Gross <[email protected]>
lkollar
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Jun 19, 2025
Use `ma_used` instead of `ma_keys->dk_nentries` for modification check so that we only check if the dictionary is modified, not if new keys are added to a different dictionary that shared the same keys object.
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Use
ma_usedinstead ofma_keys->dk_nentriesfor modification check so that we only check if the dictionary is modified, not if new keys are added to a different dictionary that shared the same keys object.dict.update()mutation check too broad #132617