Don't use PyList.get_item_unchecked() on free-threaded build#4539
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davidhewitt merged 2 commits intoPyO3:mainfrom Sep 30, 2024
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Don't use PyList.get_item_unchecked() on free-threaded build#4539davidhewitt merged 2 commits intoPyO3:mainfrom
davidhewitt merged 2 commits intoPyO3:mainfrom
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Thanks, after a bit of examination here I think that disabling this API is the right approach for now.
There's no way to guarantee that the list length remains valid from time of check to time of calling .get_item_unchecked . So the safety invariant cannot realistically be met.
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I also double-checked, and |
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Makes sense, thanks for being so thorough here!
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Followup for #4410.
get_item_uncheckedallows possible access of dangling pointers and other data races becausePyList_GET_ITEMreturns a borrowed reference. I added bindings forPyList_GetItemRefin #4410 but missed that the liter iterator usesget_item_unchecked.I could leave the APIs visible since they're already marked as unsafe, but since this API is already cfg-ed out for the limited API I thought it might make sense to disable it for free-threaded build as well.
Will add a release note if we decide disabling it is the correct thing to do.