[pointer][transmute] Migrate from util #1911

joshlf · 2024-10-15T02:37:47Z

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

This PR is on branch ptr-overhaul-more-generic-issue-1945.

We already have the merge queue; running on push is redundant.

Upgrade our MSRV to 1.65 and remove version detection logic prior to that version.

* Release 0.9.0-alpha.0 Upgrade our MSRV to 1.65 and remove version detection logic prior to that version. * Enable clippy::missing_const_for_fn While we're here, remove defensive programming against bug in `Layout::from_size_align` which is no longer needed on our new MSRV.

Now that our MSRV is 1.65, we can clean up some code. Makes progress on #67

Also clean up some code for 0.9.

* Upgrade some code for MSRV 1.65 Now that our MSRV is 1.65, we can clean up some code. Makes progress on #67 * Upgrade versions of some dependencies Now that our MSRV is 1.65, it unlocks upgrading some dependencies' versions.

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.26.12 to 3.26.13. - [Release notes](https://github.com/github/codeql-action/releases) - [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md) - [Commits](github/codeql-action@c36620d...f779452) --- updated-dependencies: - dependency-name: github/codeql-action dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [Swatinem/rust-cache](https://github.com/swatinem/rust-cache) from 2.7.3 to 2.7.5. - [Release notes](https://github.com/swatinem/rust-cache/releases) - [Changelog](https://github.com/Swatinem/rust-cache/blob/master/CHANGELOG.md) - [Commits](Swatinem/rust-cache@23bce25...82a92a6) --- updated-dependencies: - dependency-name: Swatinem/rust-cache dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Previously, we supported the `AtLeast` bound, which was used to describe a subset relationship in which `I: AtLeast<J>` implied that `I` as at least as restrictive as `J`. However, as described in #1866, this incorrectly models invariants as monotonic. In reality, invariants both provide guarantees but also *require* guarantees. This commit takes a step in the direction of resolving #1866 by removing `AtLeast`. Uses of `AtLeast<Shared>` are replaced by a new `Reference` trait, which is implemented for `Shared` and `Exclusive`. This serves two purposes: First, it makes it explicit what this bound means. Previously, `AtLeast<Shared>` had an ambiguous meaning, while `Reference` means precisely that an invariant is either `Shared` or `Exclusive` and nothing else. Second, it paves the way for #1183, in which we may add new aliasing invariants which convey ownership. In that case, it will be important for existing methods to add `Reference` bounds when those methods would not be sound in the face of ownership semantics. We also inline the items in the `invariant` module, which were previously generated by macro. The addition of the `Reference` trait did not play nicely with that macro, and we will likely need to go further from the macro in order to fix #1839 – this fix will likely require making aliasing invariants meaningfully different than other invariants, for example by adding an associated type. Makes progress on #1866

Explain why we only support concrete types so that future authors won't spuriously add support for them.

`PtrInner` carries all invariants which are not controlled by type parameters. Since `PtrInner` does not promise to uphold aliasing, alignment, or validity, we can move some utility methods to `PtrInner` which previously were responsible for maintaining invariants orthogonal to their purpose. Makes progress on #1892 (still needs to be fixed on v0.8.x) Closes #1890

This prepares us for future changes which will significantly increase the amount of code in the `invariant` module. Also merge `aliasing_safety` into this new file.

When the aliasing mode is `Any`, `Ptr<'a, T>` is invariant in `'a` and `T`. When the aliasing mode is `Shared` or `Exclusive`, `Ptr` has the same variance as `&'a T` and `&'a mut T` respectively. Makes progress on #1839

Closes #1876

`AliasingSafe` is really about whether a pointer permits unsynchronized reads - either because the referent contains no `UnsafeCell`s or because the aliasing mode is `Exclusive`. Previously, `AliasingSafe` was not named consistent with this meaning, and was a function of a *pair* of types rather than of a single type. This commit fixes both oversights. While we're here, we also add `Read` bounds in some places, allowing us to simplify many safety comments.

For aliasing, use `Inaccessible`. For alignment and validity, use `Unknown`.

This commit adds a framework which supports encoding in the type system any `I -> I` mapping where `I` is any `Invariant` type. This permits us to make `cast_unsized`'s return value smarter, and as a result, allows us to remove a lot of `unsafe` code. Makes progress on #1122

codecov-commenter · 2024-10-15T02:44:48Z

Codecov Report

Attention: Patch coverage is 32.95455% with 59 lines in your changes missing coverage. Please review.

Project coverage is 89.93%. Comparing base (99dab13) to head (2b2f66a).

Files with missing lines	Patch %	Lines
src/pointer/transmute.rs	39.18%	45 Missing ⚠️
src/util/macros.rs	0.00%	14 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1911   +/-   ##
=======================================
  Coverage   89.93%   89.93%           
=======================================
  Files          16       17    +1     
  Lines        5833     5833           
=======================================
  Hits         5246     5246           
  Misses        587      587

☔ View full report in Codecov by Sentry.
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gherrit-pr-id: I003d5360d1b7f7882a71490813eca50b39025f14

These tests depend on `src` being aligned to multiples of 2. With this commit, that dependency is explicitly enforced.

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 4 to 5. - [Release notes](https://github.com/codecov/codecov-action/releases) - [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md) - [Commits](codecov/codecov-action@v4...v5) --- updated-dependencies: - dependency-name: codecov/codecov-action dependency-type: direct:production update-type: version-update:semver-major ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.27.3 to 3.27.4. - [Release notes](https://github.com/github/codeql-action/releases) - [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md) - [Commits](github/codeql-action@396bb3e...ea9e4e3) --- updated-dependencies: - dependency-name: github/codeql-action dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [step-security/harden-runner](https://github.com/step-security/harden-runner) from 2.10.1 to 2.10.2. - [Release notes](https://github.com/step-security/harden-runner/releases) - [Commits](step-security/harden-runner@91182cc...0080882) --- updated-dependencies: - dependency-name: step-security/harden-runner dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [actions/dependency-review-action](https://github.com/actions/dependency-review-action) from 4.4.0 to 4.5.0. - [Release notes](https://github.com/actions/dependency-review-action/releases) - [Commits](actions/dependency-review-action@4081bf9...3b139cf) --- updated-dependencies: - dependency-name: actions/dependency-review-action dependency-type: direct:production update-type: version-update:semver-minor ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.27.4 to 3.27.5. - [Release notes](https://github.com/github/codeql-action/releases) - [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md) - [Commits](github/codeql-action@ea9e4e3...f09c1c0) --- updated-dependencies: - dependency-name: github/codeql-action dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.27.5 to 3.27.6. - [Release notes](https://github.com/github/codeql-action/releases) - [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md) - [Commits](github/codeql-action@f09c1c0...aa57810) --- updated-dependencies: - dependency-name: github/codeql-action dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

As of nightly-2024-11-20 - specifically [1] - this triggers an `unexpected_cfgs` lint even when emitted in derive-generated code. [1] rust-lang/rust#132577 Fixes #2117 gherrit-pr-id: I9d536f0ea08475afe0b65411b225aa55f4db449a

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.27.6 to 3.27.7. - [Release notes](https://github.com/github/codeql-action/releases) - [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md) - [Commits](github/codeql-action@aa57810...babb554) --- updated-dependencies: - dependency-name: github/codeql-action dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4.4.3 to 4.5.0. - [Release notes](https://github.com/actions/upload-artifact/releases) - [Commits](actions/upload-artifact@b4b15b8...6f51ac0) --- updated-dependencies: - dependency-name: actions/upload-artifact dependency-type: direct:production update-type: version-update:semver-minor ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.27.7 to 3.27.9. - [Release notes](https://github.com/github/codeql-action/releases) - [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md) - [Commits](github/codeql-action@babb554...df409f7) --- updated-dependencies: - dependency-name: github/codeql-action dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

gherrit-pr-id: I57f775eb6a25ab060c7f4473bac30287e01e0b68

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 is triggered when the most recent commit in a PR has a commit message which contains the string `SKIP_CARGO_SEMVER_CHECKS=1` on its own line. SKIP_CARGO_SEMVER_CHECKS=1 Closes #2083 gherrit-pr-id: Iffcecec3b7abfd48a67011d5979aa075b68da0ba

…2310) This is achieved by adding a `MaybeUninit` associated type to `KnownLayout`, whose layout is identical to `Self` except that it admits uninitialized bytes in all positions. For sized types, this is bound to `mem::MaybeUninit<Self>`. For potentially unsized structs, we synthesize a doppelganger with the same `repr`, whose leading fields are wrapped in `mem::MaybeUninit` and whose trailing field is the `MaybeUninit` associated type of struct's original trailing field type. This type-level recursion bottoms out at `[T]`, whose `MaybeUninit` associated type is bound to `[mem::MaybeUninit<T>]`. Makes progress towards #1797 SKIP_CARGO_SEMVER_CHECKS=1 gherrit-pr-id: Idfc357094e28b54a15d947141241ca2da83dcc91 Co-authored-by: Jack Wrenn <[email protected]>

Co-authored-by: usamoi <[email protected]>

This commit revises the `KnownLayout` derive on `repr(C)` target structs to preserve the correct resolution of `Self` when constructing `__ZerocopyKnownLayoutMaybeUninit`. This type contains a `MaybeUninit` version of each of the target struct's field types. Previously, it achieved this by simply copying the tokens corresponding to field types from the definition of the target struct into the definition of `__ZerocopyKnownLayoutMaybeUninit` However, on types like this: #[repr(C)] struct Struct([u8; Self::N]); …this approach is insufficient. Pasted into `__ZerocopyKnownLayoutMaybeUninit`, `Self` ceases to refer to the target struct and instead refers to `__ZerocopyKnownLayoutMaybeUninit`. To preserve `Self` hygiene, this commit defines a struct for projecting the field types of the target struct based on their index: pub unsafe trait Field<Index> { type Type: ?Sized; } …then implements it for each of the field types of the target struct; e.g.: struct Index<const N: usize>; impl Field<Index<0>> for Struct { type Type = [u8; Self::N]; } With this, the fields of `__ZerocopyKnownLayoutMaybeUninit` can be defined hygienically; e.g., as `<Struct as Field<0>>::Type`. Fixes #2116 Co-authored-by: Jack Wrenn <[email protected]>

Fixes #2302 gherrit-pr-id: If68c1724be15c4df3ec936a12cf854908650a639 Co-authored-by: Joshua Liebow-Feeser <[email protected]>

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

joshlf and others added 20 commits October 12, 2024 14:06

[ci] Don't run on push (#1882)

5b5d5a6

We already have the merge queue; running on push is redundant.

Release 0.9.0-alpha.0 (#1881)

e7217b5

Upgrade our MSRV to 1.65 and remove version detection logic prior to that version.

Upgrade some code for MSRV 1.65 (#1885)

1788f44

Now that our MSRV is 1.65, we can clean up some code. Makes progress on #67

Clean up some code for new MSRV (#1888)

7349fe0

Also clean up some code for 0.9.

Upgrade versions of some dependencies (#1886)

19ab41c

* Upgrade some code for MSRV 1.65 Now that our MSRV is 1.65, we can clean up some code. Makes progress on #67 * Upgrade versions of some dependencies Now that our MSRV is 1.65, it unlocks upgrading some dependencies' versions.

Roll pinned toolchains on v0.8.x branch (#1887)

5452c3d

[ci] Roll pinned nightly toolchain (#1900)

2e819ac

[ci] Roll pinned nightly toolchain (#1902)

ccf477d

[derive] Document trivial_is_bit_valid (#1905)

967b3a0

Explain why we only support concrete types so that future authors won't spuriously add support for them.

[pointer][invariant] Move to separate file (#1906)

ca9243f

This prepares us for future changes which will significantly increase the amount of code in the `invariant` module. Also merge `aliasing_safety` into this new file.

[pointer] Match variance of references (#1894)

51475bd

When the aliasing mode is `Any`, `Ptr<'a, T>` is invariant in `'a` and `T`. When the aliasing mode is `Shared` or `Exclusive`, `Ptr` has the same variance as `&'a T` and `&'a mut T` respectively. Makes progress on #1839

[pointer] Make invariants opaque, more ergonomic (#1895)

f80a65d

Closes #1876

[pointer] Rename Any -> Unknown/Inaccessible (#1909)

ae43fce

For aliasing, use `Inaccessible`. For alignment and validity, use `Unknown`.

This was referenced Oct 15, 2024

[pointer][transmute] Support generic TransmuteFrom #1910

Open

[pointer][transmute] Migrate from util #1898

Closed

This was referenced Oct 15, 2024

[WIP] Add Self: Read bound to is_bit_valid #1912

Open

[pointer] Support Box and Arc #1913

Open

[ci] Roll pinned nightly toolchain (#1915)

77a5f56

jswrenn approved these changes Oct 15, 2024

View reviewed changes

joshlf force-pushed the Ifc49755af0d90eeefe7822d755d508403c266bda branch from 3b9ac7b to c88e77f Compare October 15, 2024 14:15

joshlf and others added 2 commits October 15, 2024 17:17

Remove items deprecated in 0.8 (#1916)

49749b7

gherrit-pr-id: I003d5360d1b7f7882a71490813eca50b39025f14

Fix flaky TryFromBytes tests (#1917)

f04c344

These tests depend on `src` being aligned to multiples of 2. With this commit, that dependency is explicitly enforced.

dependabot bot and others added 13 commits November 15, 2024 15:37

[ci] Roll pinned stable toolchain (#2120)

de1c6d8

[derive] Don't emit #[cfg(coverage_nightly)] (#2123) (#2126)

9a2fce6

As of nightly-2024-11-20 - specifically [1] - this triggers an `unexpected_cfgs` lint even when emitted in derive-generated code. [1] rust-lang/rust#132577 Fixes #2117 gherrit-pr-id: I9d536f0ea08475afe0b65411b225aa55f4db449a

[ci] Roll pinned stable toolchain (#2225)

98b95d3

gherrit-pr-id: I57f775eb6a25ab060c7f4473bac30287e01e0b68

[ci] Roll pinned stable toolchain (#2281)

77846a9

joshlf force-pushed the Ifc49755af0d90eeefe7822d755d508403c266bda branch 2 times, most recently from 0948d1a to 75208cb Compare February 5, 2025 19:55

joshlf changed the base branch from main to I1ac2ae177a235083e33b09fc848423220d3da042 February 5, 2025 19:56

joshlf mentioned this pull request Feb 5, 2025

[pointer][invariant] Remove AliasingMapping, Inaccessible #2301

Merged

joshlf force-pushed the Ifc49755af0d90eeefe7822d755d508403c266bda branch from 75208cb to 93d0d13 Compare February 5, 2025 20:23

joshlf force-pushed the I1ac2ae177a235083e33b09fc848423220d3da042 branch from 08771d7 to 03a15c4 Compare February 5, 2025 20:23

Base automatically changed from I1ac2ae177a235083e33b09fc848423220d3da042 to main February 5, 2025 20:58

joshlf force-pushed the Ifc49755af0d90eeefe7822d755d508403c266bda branch from 93d0d13 to 2b2f66a Compare February 5, 2025 23:35

joshlf and others added 6 commits February 6, 2025 19:06

Implement KnownLayout for f16 and f128 (#2250) (#2312)

64df858

Co-authored-by: usamoi <[email protected]>

[derive] Fix bug with KnownLayout on repr(packed) (#2307) (#2317)

17e7e4d

Fixes #2302 gherrit-pr-id: If68c1724be15c4df3ec936a12cf854908650a639 Co-authored-by: Joshua Liebow-Feeser <[email protected]>

[pointer][transmute] Migrate from util

34eb2a3

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

joshlf force-pushed the Ifc49755af0d90eeefe7822d755d508403c266bda branch from 2b2f66a to 34eb2a3 Compare February 7, 2025 19:35

joshlf force-pushed the main branch from 8ee868d to fe70ab6 Compare February 25, 2025 22:07

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[pointer][transmute] Migrate from util #1911

[pointer][transmute] Migrate from util #1911

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