[3.15] gh-158254: Detect keys changing during reverse dict iteration (GH-158255) - #158267
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…ythonGH-158255) A reverse dict iterator only checked that the dict's size was unchanged, so after the keys were replaced with the same number of keys it kept yielding entries for the new keys. It could yield more items than the dict had when it was created, and __length_hint__() then wrapped around. Add the check the forward iterators already have: finding an entry after the expected number of items raises "dictionary keys changed during iteration". (cherry picked from commit 042a7c150552a4ddb5a90cf65a6e5b9e7ba3f7dc) Co-authored-by: Joshua Bronson <jabronson@gmail.com> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
miss-islington
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markshannon and
methane
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September 27, 2026 02:53
ZeroIntensity
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Sep 27, 2026
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A reverse dict iterator only checked that the dict's size was unchanged,
so after the keys were replaced with the same number of keys it kept
yielding entries for the new keys. It could yield more items than the
dict had when it was created, and length_hint() then wrapped around.
Add the check the forward iterators already have: finding an entry after
the expected number of items raises "dictionary keys changed during
iteration".
(cherry picked from commit 042a7c1)
Co-authored-by: Joshua Bronson jabronson@gmail.com
Co-authored-by: Claude Opus 5.5 noreply@anthropic.com