Add MaybeUninit::(slice_)as_bytes(_mut) by Amanieu · Pull Request #89747 · rust-...
source link: https://github.com/rust-lang/rust/pull/89747
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This seems related to some of the questions that have come up in the safe transmute work.
For the mut versions, this allows writing arbitrary data to a value or slice. That data still won't become usable until a call to assume_init, which is unsafe, so this isn't unsound, but as far as I know, doing something like that would previously have required mem::transmute.
In either case, this would make it very easy to rely on the internal layout of a type, which a crate may not have intended to make public. So at the very least, I think we need a comment noting that the ability to access the bytes of private fields or the exact layout of a structure does not necessarily make those details part of a crate's stable ABI.
I don't have any objections to these methods existing; I just want to make sure we note (and where appropriate document) what new capabilities these methods expose, and the potential hazards associated with them.
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