[pointer][transmute] Support generic TransmuteFrom #1965
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This prepares us to rename `TransparentWrapper` to `TransmuteFrom`, which we'll do in a follow-up commit to preserve nice git diffs. Makes progress on #1122 gherrit-pr-id: Ifc49755af0d90eeefe7822d755d508403c266bda
We previously used `AliasingMapping`s and `Inaccessible` to model `UnsafeCell` agreement. This abuses the notion of a mapping since one doesn't ever actually want to change the aliasing of a pointer (and certainly not to `Inaccessible`) - really this was meant to model pointer casts which should never be performed. In addition to being an awkward fit, the presence of `Inaccessible` meant that code could not assume that any `Aliasing` invariant permitted reading, and so we had to add extra machinery to work around this. Future commits will use a different, simpler model for denoting `UnsafeCell` agreement or disagreement. While we're here, make `Read` slightly more permissive, implemented for `A: Aliasing, T: Immutable` rather than just `A: Reference, T: Immutable`. Makes progress on #1122, #1866 gherrit-pr-id: I1ac2ae177a235083e33b09fc848423220d3da042
This commit replaces the `TransparentWrapper` trait with a more generic, bidirectional `TransmuteFrom<T>` trait. `U: TransmuteFrom<T>` indicates that `T` and `U` have the same sizes and that `T` can be transmuted into `U` given certain alignment and validity invariant mappings. Makes progress on #1122 gherrit-pr-id: I3a6abe00c9220431e60f9beee68e472d323b5612
This was referenced Oct 22, 2024
joshlf
force-pushed
the
I1ac2ae177a235083e33b09fc848423220d3da042
branch
2 times, most recently
from
33fc89f
to
48f1450
Compare
joshlf
force-pushed
the
I1ac2ae177a235083e33b09fc848423220d3da042
branch
from
48f1450
to
355531d
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This commit replaces the
TransparentWrappertrait with a more generic,bidirectional
TransmuteFrom<T>trait.U: TransmuteFrom<T>indicatesthat
TandUhave the same sizes and thatTcan be transmuted intoUgiven certain alignment and validity invariant mappings.Makes progress on #1122
This PR is on branch ptr-overhaul.