Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Improve ManuallyDoc safety comments #522

Merged
merged 1 commit into from
Oct 19, 2023
Merged

Improve ManuallyDoc safety comments #522

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
31 changes: 25 additions & 6 deletions src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -652,9 +652,18 @@ impl_known_layout!(const N: usize, T => [T; N]);

safety_comment! {
/// SAFETY:
/// `str` and `ManuallyDrop<[T]>` have the same representations as `[u8]`
/// and `[T]` repsectively. `str` has different bit validity than `[u8]`,
/// but that doesn't affect the soundness of this impl.
/// `str` and `ManuallyDrop<[T]>` [1] have the same representations as
/// `[u8]` and `[T]` repsectively. `str` has different bit validity than
/// `[u8]`, but that doesn't affect the soundness of this impl.
///
/// [1] Per https://doc.rust-lang.org/nightly/core/mem/struct.ManuallyDrop.html:
///
/// `ManuallyDrop<T>` is guaranteed to have the same layout and bit
/// validity as `T`
///
/// TODO(#429): Once this text (added in
/// https://github.com/rust-lang/rust/pull/115522) is available on stable,
/// quote the stable docs instead of the nightly docs.
unsafe_impl_known_layout!(#[repr([u8])] str);
unsafe_impl_known_layout!(T: ?Sized + KnownLayout => #[repr(T)] ManuallyDrop<T>);
}
Expand Down Expand Up @@ -1496,9 +1505,10 @@ safety_comment! {
}
safety_comment! {
/// SAFETY:
/// `ManuallyDrop` has the same layout as `T`, and accessing the inner value
/// is safe (meaning that it's unsound to leave the inner value
/// uninitialized while exposing the `ManuallyDrop` to safe code).
/// `ManuallyDrop` has the same layout and bit validity as `T` [1], and
/// accessing the inner value is safe (meaning that it's unsound to leave
/// the inner value uninitialized while exposing the `ManuallyDrop` to safe
/// code).
/// - `FromZeroes`, `FromBytes`: Since it has the same layout as `T`, any
/// valid `T` is a valid `ManuallyDrop<T>`. If `T: FromZeroes`, a sequence
/// of zero bytes is a valid `T`, and thus a valid `ManuallyDrop<T>`. If
Expand All @@ -1511,6 +1521,15 @@ safety_comment! {
/// code can only ever access a `ManuallyDrop` with all initialized bytes.
/// - `Unaligned`: `ManuallyDrop` has the same layout (and thus alignment)
/// as `T`, and `T: Unaligned` guarantees that that alignment is 1.
///
/// [1] Per https://doc.rust-lang.org/nightly/core/mem/struct.ManuallyDrop.html:
///
/// `ManuallyDrop<T>` is guaranteed to have the same layout and bit
/// validity as `T`
///
/// TODO(#429): Once this text (added in
/// https://github.com/rust-lang/rust/pull/115522) is available on stable,
/// quote the stable docs instead of the nightly docs.
unsafe_impl!(T: ?Sized + FromZeroes => FromZeroes for ManuallyDrop<T>);
unsafe_impl!(T: ?Sized + FromBytes => FromBytes for ManuallyDrop<T>);
unsafe_impl!(T: ?Sized + AsBytes => AsBytes for ManuallyDrop<T>);
Expand Down