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document zerocopy's relationship to Project Safe Transmute #484

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document zerocopy's relationship to Project Safe Transmute #484

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23 changes: 23 additions & 0 deletions README.md
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Expand Up @@ -107,6 +107,29 @@ memory model, and *any future memory model*. We ensure this by:
[Miri]: https://github.com/rust-lang/miri
[Kani]: https://github.com/model-checking/kani

## Relationship to Project Safe Transmute

[Project Safe Transmute] is an official initiative of the Rust Project to
develop language-level support for safer transmutation. The Project consults
with crates like zerocopy to identify aspects of safer transmutation that
would benefit from compiler support, and has developed an [experimental,
compiler-supported analysis][mcp-transmutability] which determines whether,
for a given type, any value of that type may be soundly transmuted into
another type. Once this functionality is sufficiently mature, zerocopy
intends to replace its internal transmutability analysis (implemented by our
custom derives) with the compiler-supported one. This change will likely be
an implementation detail that is invisible to zerocopy's users.

Project Safe Transmute will not replace the need for most of zerocopy's
higher-level abstractions. The experimental compiler analysis is a tool for
checking the soundness of `unsafe` code, not a tool to avoid writing
`unsafe` code altogether. For the foreseeable future, crates like zerocopy
will still be required in order to provide higher-level abstractions on top
of the building block provided by Project Safe Transmute.

[Project Safe Transmute]: https://rust-lang.github.io/rfcs/2835-project-safe-transmute.html
[mcp-transmutability]: https://github.com/rust-lang/compiler-team/issues/411

## Disclaimer

Disclaimer: Zerocopy is not an officially supported Google product.
23 changes: 23 additions & 0 deletions src/lib.rs
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Expand Up @@ -105,6 +105,29 @@
//!
//! [Miri]: https://github.com/rust-lang/miri
//! [Kani]: https://github.com/model-checking/kani
//!
//! # Relationship to Project Safe Transmute
//!
//! [Project Safe Transmute] is an official initiative of the Rust Project to
//! develop language-level support for safer transmutation. The Project consults
//! with crates like zerocopy to identify aspects of safer transmutation that
//! would benefit from compiler support, and has developed an [experimental,
//! compiler-supported analysis][mcp-transmutability] which determines whether,
//! for a given type, any value of that type may be soundly transmuted into
//! another type. Once this functionality is sufficiently mature, zerocopy
//! intends to replace its internal transmutability analysis (implemented by our
//! custom derives) with the compiler-supported one. This change will likely be
//! an implementation detail that is invisible to zerocopy's users.
//!
//! Project Safe Transmute will not replace the need for most of zerocopy's
//! higher-level abstractions. The experimental compiler analysis is a tool for
//! checking the soundness of `unsafe` code, not a tool to avoid writing
//! `unsafe` code altogether. For the foreseeable future, crates like zerocopy
//! will still be required in order to provide higher-level abstractions on top
//! of the building block provided by Project Safe Transmute.
//!
//! [Project Safe Transmute]: https://rust-lang.github.io/rfcs/2835-project-safe-transmute.html
//! [mcp-transmutability]: https://github.com/rust-lang/compiler-team/issues/411

// Sometimes we want to use lints which were added after our MSRV.
// `unknown_lints` is `warn` by default and we deny warnings in CI, so without
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