gh-115398: Revert PyExpat_CAPI_MAGIC version bump
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…eferralEnabled addition (pythonGH-116301)" This reverts part of commit eda2963.
AlexWaygood
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PyExpat_CAPI_MAGIC version bumpPyExpat_CAPI_MAGIC version bump
serhiy-storchaka
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Mar 6, 2024
gpshead
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Mar 6, 2024
adorilson
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…16411) Revert "pythongh-115398: Increment PyExpat_CAPI_MAGIC for SetReparseDeferralEnabled addition (pythonGH-116301)" This reverts part of commit eda2963. Why? this comment buried in an earlier code review explains: I checked again how that value is used in practice, it's here: https://github.com/python/cpython/blob/0c80da4c14d904a367968955544dd6ae58c8101c/Modules/_elementtree.c#L4363-L4372 Based on that code my understanding is that loading bigger structs from the future is considered okay unless `PyExpat_CAPI_MAGIC` differs, which implies that (1) magic needs to stay the same to support loading the future from the past and (2) that `PyExpat_CAPI_MAGIC` should only ever change for changes that do not increase size (but keep it constant). To summarize, that supports your argument. I checked branches 3.8, 3.9, 3.10, 3.11, 3.12 now and they all have the same comparison code there so reverting that magic string bump will support seamless backporting.
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…16411) Revert "pythongh-115398: Increment PyExpat_CAPI_MAGIC for SetReparseDeferralEnabled addition (pythonGH-116301)" This reverts part of commit eda2963. Why? this comment buried in an earlier code review explains: I checked again how that value is used in practice, it's here: https://github.com/python/cpython/blob/0c80da4c14d904a367968955544dd6ae58c8101c/Modules/_elementtree.c#L4363-L4372 Based on that code my understanding is that loading bigger structs from the future is considered okay unless `PyExpat_CAPI_MAGIC` differs, which implies that (1) magic needs to stay the same to support loading the future from the past and (2) that `PyExpat_CAPI_MAGIC` should only ever change for changes that do not increase size (but keep it constant). To summarize, that supports your argument. I checked branches 3.8, 3.9, 3.10, 3.11, 3.12 now and they all have the same comparison code there so reverting that magic string bump will support seamless backporting.
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This reverts part of commit eda2963 from #116301 because it is both hurting and unnecessary, #115623 (comment) explains in detail why.
CC @encukou @gpshead @serhiy-storchaka (alphabetical order)
PS: Could someone add label
skip-newsfor me please, I lack permissions to. Thanks! 🙏XML_SetReparseDeferralEnabled#115398