[proofs] Initial commit #652
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joshlf
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jswrenn
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| /// field, which is `pub`. Per the reference [2], this means that the | ||
| /// `#[repr(transparent)]` attribute is "considered part of the public ABI". | ||
| /// `Wrapping<T>` is `#[repr(transparent)]` and has a single `T` field, | ||
| /// which is `pub`. [1] Per axiom-repr-transparent-layout-validity, we may |
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Should axiom-repr-transparent-layout-validity perhaps be a intradoc link? It'd give us a modest defense against proof rot.
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Oooh good idea. I'll also need to make sure that our safety doc comments are actually being parsed by rustdoc.
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| //! ## transparent-layout-validity | ||
| //! | ||
| //! A type, `T`, has the property `transparent-layout-validity(U)` if the | ||
| //! following all hold: | ||
| //! - `T` and `U` have the same alignment | ||
| //! - For all `t: *const T`, `let u = t as *const U` is valid and | ||
| //! `size_of_val_raw(t) == size_of_val_raw(u)`. | ||
| //! - For all `u: *const U`, `let t = *const T` is valid and `size_of_val_raw(u) | ||
| //! == size_of_val_raw(t)`. | ||
| //! - For all `(t, u): (*const T, *const U)` where `size_of_val_raw(t) == | ||
| //! size_of_val_raw(u)`: | ||
| //! - `t` and `u` refer to `UnsafeCell`s at the same byte ranges. | ||
| //! - If `*t` contains a valid `T`, that implies that `*u` contains a valid | ||
| //! `U`. | ||
| //! - If `*u` contains a valid `U`, that implies that `*t` contains a valid | ||
| //! `T`. |
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Concretely:
/// A type, `T`, has the property `transparent-layout-validity(U)` if the
/// following all hold:
/// - `T` and `U` have the same alignment
/// - For all `t: *const T`, `let u = t as *const U` is valid and
/// `size_of_val_raw(t) == size_of_val_raw(u)`.
/// - For all `u: *const U`, `let t = *const T` is valid and `size_of_val_raw(u)
/// == size_of_val_raw(t)`.
/// - For all `(t, u): (*const T, *const U)` where `size_of_val_raw(t) ==
/// size_of_val_raw(u)`:
/// - `t` and `u` refer to `UnsafeCell`s at the same byte ranges.
/// - If `*t` contains a valid `T`, that implies that `*u` contains a valid
/// `U`.
/// - If `*u` contains a valid `U`, that implies that `*t` contains a valid
/// `T`.
#[allow(unsused)] // This only exists as an anchor for intradoc links.
const TRANSPARENT_LAYOUT_VALIDIDTY: () = ();
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Add axioms and lemmas which are useful in proving the soundness of some trait impls. Makes progress on #429
joshlf
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Add axioms and lemmas which are useful in proving the soundness of some trait impls.
Makes progress on #429