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Implement traits for some atomic types #1010

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71 changes: 70 additions & 1 deletion src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,10 @@ use core::{
ops::{Deref, DerefMut},
ptr::{self, NonNull},
slice,
sync::atomic::{
AtomicBool, AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicPtr, AtomicU16,
AtomicU32, AtomicU64, AtomicU8, AtomicUsize,
},
};

use crate::pointer::invariant;
Expand Down Expand Up @@ -1096,10 +1100,13 @@ impl_known_layout!(
u8, i8, u16, i16, u32, i32, u64, i64, u128, i128, usize, isize, f32, f64,
bool, char,
NonZeroU8, NonZeroI8, NonZeroU16, NonZeroI16, NonZeroU32, NonZeroI32,
NonZeroU64, NonZeroI64, NonZeroU128, NonZeroI128, NonZeroUsize, NonZeroIsize
NonZeroU64, NonZeroI64, NonZeroU128, NonZeroI128, NonZeroUsize, NonZeroIsize,
AtomicBool, AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16,
AtomicU32, AtomicU64, AtomicU8, AtomicUsize
);
#[rustfmt::skip]
impl_known_layout!(
T => AtomicPtr<T>,
T => Option<T>,
T: ?Sized => PhantomData<T>,
T => Wrapping<T>,
Expand Down Expand Up @@ -3809,6 +3816,55 @@ safety_comment! {
unsafe_impl!(Option<NonZeroIsize>: TryFromBytes, FromZeros, FromBytes, IntoBytes);
}

safety_comment! {
/// SAFETY:
/// Per [1], `AtomicBool` has the same size, alignment, and bit validity as
/// `bool`. `bool` implements `IntoBytes` and `Unaligned`.
///
/// [1] TODO(#896), TODO(https://github.com/rust-lang/rust/pull/121943):
/// Cite docs once they've landed.
unsafe_impl!(AtomicBool: IntoBytes, Unaligned);
/// SAFETY: Per [1], `AtomicU8` and `AtomicI8` have the same size and bit
/// validity as `u8` and `i8` respectively. `u8` and `i8` both implement
/// `TryFromBytes` (with no validator), `FromZeros`, `FromBytes`, and
/// `IntoBytes`.
///
/// While alignment is not documented, we know that `AtomicU8` and
/// `AtomicI8` are each 1 byte in size (since they have the same size as
/// `u8` and `i8`). Since size must be a multiple of alignment [2], this
/// means that their alignments cannot be greater than 1, and since
/// alignment cannot be less than 1 [3], their alignments must be exactly 1.
/// Thus, they can soundly implement `Unaligned`.
///
/// [1] TODO(#896), TODO(https://github.com/rust-lang/rust/pull/121943):
/// Cite docs once they've landed.
///
/// [3] Per https://doc.rust-lang.org/reference/type-layout.html#size-and-alignment:
///
/// The size of a value is always a multiple of its alignment.
///
/// [2] Per https://doc.rust-lang.org/reference/type-layout.html#size-and-alignment:
///
/// Alignment is measured in bytes, and must be at least 1.
unsafe_impl!(AtomicU8: TryFromBytes, FromZeros, FromBytes, IntoBytes, Unaligned);
unsafe_impl!(AtomicI8: TryFromBytes, FromZeros, FromBytes, IntoBytes, Unaligned);
/// SAFETY: Per [1], these types have the same size and bit validity as
/// their respective primitive types. All of these primitive types implement
/// `TryFromBytes` (with no validator), `FromZeros`, `FromBytes`, and
/// `IntoBytes`.
///
/// [1] TODO(#896), TODO(https://github.com/rust-lang/rust/pull/121943):
/// Cite docs once they've landed.
unsafe_impl!(AtomicU16: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicU32: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicU64: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicUsize: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicI16: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicI32: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicI64: TryFromBytes, FromZeros, FromBytes, IntoBytes);
unsafe_impl!(AtomicIsize: TryFromBytes, FromZeros, FromBytes, IntoBytes);
}

safety_comment! {
/// SAFETY:
/// While it's not fully documented, the consensus is that `Box<T>` does not
Expand Down Expand Up @@ -9109,6 +9165,19 @@ mod tests {
assert_impls!(Option<NonZeroUsize>: KnownLayout, NoCell, TryFromBytes, FromZeros, FromBytes, IntoBytes, !Unaligned);
assert_impls!(Option<NonZeroIsize>: KnownLayout, NoCell, TryFromBytes, FromZeros, FromBytes, IntoBytes, !Unaligned);

assert_impls!(AtomicBool: KnownLayout, IntoBytes, Unaligned, !TryFromBytes, !FromZeros, !FromBytes, !NoCell);
assert_impls!(AtomicU8: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, Unaligned, !NoCell);
assert_impls!(AtomicI8: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, Unaligned, !NoCell);
assert_impls!(AtomicU16: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicU32: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicU64: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicUsize: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicI16: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicI32: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicI64: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicIsize: KnownLayout, TryFromBytes, FromZeros, FromBytes, IntoBytes, !NoCell, !Unaligned);
assert_impls!(AtomicPtr<NotZerocopy>: KnownLayout, !TryFromBytes, !FromZeros, !FromBytes, !IntoBytes, !NoCell, !Unaligned);

// Implements none of the ZC traits.
struct NotZerocopy;

Expand Down