diff options
| author | Nilstrieb <48135649+Nilstrieb@users.noreply.github.com> | 2022-05-20 20:48:29 +0200 |
|---|---|---|
| committer | Nilstrieb <48135649+Nilstrieb@users.noreply.github.com> | 2022-05-26 21:28:07 +0200 |
| commit | e7c468dc594c475b886280aa7e56779b279d0dbb (patch) | |
| tree | 2518e1c879a543c48ba3dbd05eb4df219dc57599 /library/alloc | |
| parent | 1851f0802e148bb7fa0bfd7dabcb7397bf371b0b (diff) | |
Document the current aliasing rules for `Box<T>`.
Currently, `Box<T>` gets `noalias`, meaning it has the same rules as `&mut T`. This is sparsely documented, even though it can have quite a big impact on unsafe code using box. Therefore, these rules are documented here, with a big warning that they are not normative and subject to change, since we have not yet committed to an aliasing model and the state of `Box<T>` is especially uncertain.
Diffstat (limited to 'library/alloc')
| -rw-r--r-- | library/alloc/src/boxed.rs | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs index c07536f0d0c..9818cb352ca 100644 --- a/library/alloc/src/boxed.rs +++ b/library/alloc/src/boxed.rs @@ -122,7 +122,21 @@ //! definition is just using `T*` can lead to undefined behavior, as //! described in [rust-lang/unsafe-code-guidelines#198][ucg#198]. //! +//! # Considerations for unsafe code +//! +//! **Warning: This section is not normative and is subject to change, possibly +//! being relaxed in the future! It is a simplified summary of the rules +//! currently implemented in the compiler.** +//! +//! The aliasing rules for `Box<T>` are the same as for `&mut T`. `Box<T>` +//! asserts uniqeness over its content. Using raw pointers derived from a box +//! after that box has been mutated through, moved or borrowed as `&mut T` +//! is not allowed. For more guidance on working with box from unsafe code, see +//! [rust-lang/unsafe-code-guidelines#326][ucg#326]. +//! +//! //! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198 +//! [ucg#326]: https://github.com/rust-lang/unsafe-code-guidelines/issues/326 //! [dereferencing]: core::ops::Deref //! [`Box::<T>::from_raw(value)`]: Box::from_raw //! [`Global`]: crate::alloc::Global |