bitshifter / glam-rs / 36212371374

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Build Type

push

github

Committed by web-flow

Commit Message

feat: add a `rkyv-08` feature with dedicated portable archived types (#869)

## Objective

Add the dedicated archived types from #766 without changing the existing
`rkyv`
feature. #766 changed `rkyv` in place, which is breaking; here the new
impls go
on a new `rkyv-08` feature, the old impls will be removed in the next
major
release of glam.

Supersedes #766 (@MarijnS95)

Fixes #844 

## Solution

Opt in with `rkyv-08`:

```toml
glam = { version = "0.33", features = ["rkyv-08"] }
```

- `rkyv-08` archives each `glam` type to its own `Archived*` counterpart
built
from `rkyv`'s archived primitives, exposed at `glam::rkyv_08`. The
archived
  element type follows `rkyv`'s `unaligned` and `big_endian` features.
- The archived types implement `bytemuck::Pod`/`Zeroable`, convert to
and from
the native type with `From`, and get `Archive::COPY_OPTIMIZATION` where
the
archived form is a byte-for-byte copy of the native one. `Portable` and
  `NoUndef` are only implemented where the archived type really has that
  property.
- `rkyv` keeps the previous impls, in `src/features/impl_rkyv.rs`, which
are now
  documented as unsound and will be removed in the next major release.
- The dependency is renamed `rkyv-08 = { package = "rkyv", version =
"0.8" }`
  following #857, matching `encase-012`/`encase-013`.
- `bytecheck` works with either feature.
- If both are enabled the `rkyv-08` impls are used; the two sets cannot
compile
together because both implement `rkyv` 0.8's `Archive` for the same
types, so
the old impls are gated on `all(feature = "rkyv", not(feature =
"rkyv-08"))`.

The old impls are unsound because they claim `Portable` for layouts that
differ
between targets (`Vec3A`/`Mat3A`/`Affine3A` alignment, `Affine2` tail
padding,
`Vec3A` padding under `scalar-math`) and `NoUndef` for types with
padding, so
archives copied uninitialised bytes and depended on the native
endianness and
the SIMD backend.

## Migration

No breaking change. Replace `rkyv` with `rkyv-0... (continued)

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