core::marker::Sync - Rust
Description: API documentation for the Rust `Sync` trait in crate `core`.
Keywords: rust, rustlang, rust-lang, Sync

# 1.0.0[−][src]Trait core::marker::Sync

    #[lang = "sync"]pub unsafe auto trait Sync { }

Types for which it is safe to share references between threads.

This trait is automatically implemented when the compiler determines it's appropriate.

The precise definition is: a type `T` is `Sync` if and only if `&T` is `Send`. In other words, if there is no possibility of undefined behavior (including data races) when passing `&T` references between threads.

As one would expect, primitive types like `u8` and `f64` are all `Sync`, and so are simple aggregate types containing them, like tuples, structs and enums. More examples of basic `Sync` types include "immutable" types like `&T`, and those with simple inherited mutability, such as `Box<T>`, `Vec<T>` and most other collection types. (Generic parameters need to be `Sync` for their container to be `Sync`.)

A somewhat surprising consequence of the definition is that `&mut T` is `Sync` (if `T` is `Sync`) even though it seems like that might provide unsynchronized mutation. The trick is that a mutable reference behind a shared reference (that is, `& &mut T`) becomes read-only, as if it were a `& &T`. Hence there is no risk of a data race.

Types that are not `Sync` are those that have "interior mutability" in a non-thread-safe form, such as `Cell` and `RefCell`. These types allow for mutation of their contents even through an immutable, shared reference. For example the `set` method on `Cell<T>` takes `&self`, so it requires only a shared reference `&Cell<T>`. The method performs no synchronization, thus `Cell` cannot be `Sync`.

Another example of a non-`Sync` type is the reference-counting pointer `Rc`. Given any reference `&Rc<T>`, you can clone a new `Rc<T>`, modifying the reference counts in a non-atomic way.

For cases when one does need thread-safe interior mutability, Rust provides atomic data types, as well as explicit locking via `sync::Mutex` and `sync::RwLock`. These types ensure that any mutation cannot cause data races, hence the types are `Sync`. Likewise, `sync::Arc` provides a thread-safe analogue of `Rc`.

Any types with interior mutability must also use the `cell::UnsafeCell` wrapper around the value(s) which can be mutated through a shared reference. Failing to doing this is undefined behavior. For example, `transmute`-ing from `&T` to `&mut T` is invalid.

See the Nomicon for more details about `Sync`.

## Implementors

### `impl Sync for AtomicBool`[src]

### `impl Sync for AtomicI8`[src]

### `impl Sync for AtomicI16`[src]

### `impl Sync for AtomicI32`[src]

### `impl Sync for AtomicI64`[src]

### `impl Sync for AtomicI128`[src]

### `impl Sync for AtomicIsize`[src]

### `impl Sync for AtomicU8`[src]

### `impl Sync for AtomicU16`[src]

### `impl Sync for AtomicU32`[src]

### `impl Sync for AtomicU64`[src]

### `impl Sync for AtomicU128`[src]

### `impl Sync for AtomicUsize`[src]

### `impl Sync for Waker`[src]

### `impl<T> Sync for Empty<T>`[src]

### `impl<T> Sync for AtomicPtr<T>`[src]

### `impl<T: Sync> Sync for core::slice::Iter<'_, T>`[src]

### `impl<T: Sync> Sync for core::slice::IterMut<'_, T>`[src]

### `impl<T: ?Sized> !Sync for *const T`[src]

### `impl<T: ?Sized> !Sync for *mut T`[src]

### `impl<T: ?Sized> !Sync for Cell<T>`[src]

### `impl<T: ?Sized> !Sync for RefCell<T>`[src]

### `impl<T: ?Sized> !Sync for UnsafeCell<T>`[src]

### `impl<T: ?Sized> !Sync for NonNull<T>`[src]

`NonNull` pointers are not `Sync` because the data they reference may be aliased.

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## Auto implementors

### `impl !Sync for TraitObject`[src]

### `impl !Sync for RawWaker`[src]

### `impl Sync for core::cmp::Ordering`[src]

### `impl Sync for Infallible`[src]

### `impl Sync for c_void`[src]

### `impl Sync for Alignment`[src]

### `impl Sync for FpCategory`[src]

### `impl Sync for IntErrorKind`[src]

### `impl Sync for SearchStep`[src]

### `impl Sync for core::sync::atomic::Ordering`[src]

### `impl Sync for AllocError`[src]

### `impl Sync for Layout`[src]

### `impl Sync for LayoutError`[src]

### `impl Sync for TypeId`[src]

### `impl Sync for float64x1_t`[src]

### `impl Sync for float64x2_t`[src]

### `impl Sync for int8x16x2_t`[src]

### `impl Sync for int8x16x3_t`[src]

### `impl Sync for int8x16x4_t`[src]

### `impl Sync for poly8x16x2_t`[src]

### `impl Sync for poly8x16x3_t`[src]

### `impl Sync for poly8x16x4_t`[src]

### `impl Sync for uint8x16x2_t`[src]

### `impl Sync for uint8x16x3_t`[src]

### `impl Sync for uint8x16x4_t`[src]

### `impl Sync for ISH`[src]

### `impl Sync for ISHLD`[src]

### `impl Sync for ISHST`[src]

### `impl Sync for LD`[src]

### `impl Sync for NSH`[src]

### `impl Sync for NSHLD`[src]

### `impl Sync for NSHST`[src]

### `impl Sync for OSH`[src]

### `impl Sync for OSHLD`[src]

### `impl Sync for OSHST`[src]

### `impl Sync for ST`[src]

### `impl Sync for SY`[src]

### `impl Sync for float32x2_t`[src]

### `impl Sync for float32x4_t`[src]

### `impl Sync for int8x8_t`[src]

### `impl Sync for int8x8x2_t`[src]

### `impl Sync for int8x8x3_t`[src]

### `impl Sync for int8x8x4_t`[src]

### `impl Sync for int8x16_t`[src]

### `impl Sync for int16x4_t`[src]

### `impl Sync for int16x8_t`[src]

### `impl Sync for int32x2_t`[src]

### `impl Sync for int32x4_t`[src]

### `impl Sync for int64x1_t`[src]

### `impl Sync for int64x2_t`[src]

### `impl Sync for poly8x8_t`[src]

### `impl Sync for poly8x8x2_t`[src]

### `impl Sync for poly8x8x3_t`[src]

### `impl Sync for poly8x8x4_t`[src]

### `impl Sync for poly8x16_t`[src]

### `impl Sync for poly16x4_t`[src]

### `impl Sync for poly16x8_t`[src]

### `impl Sync for poly64x1_t`[src]

### `impl Sync for poly64x2_t`[src]

### `impl Sync for uint8x8_t`[src]

### `impl Sync for uint8x8x2_t`[src]

### `impl Sync for uint8x8x3_t`[src]

### `impl Sync for uint8x8x4_t`[src]

### `impl Sync for uint8x16_t`[src]

### `impl Sync for uint16x4_t`[src]

### `impl Sync for uint16x8_t`[src]

### `impl Sync for uint32x2_t`[src]

### `impl Sync for uint32x4_t`[src]

### `impl Sync for uint64x1_t`[src]

### `impl Sync for uint64x2_t`[src]

### `impl Sync for vector_bool_long`[src]

### `impl Sync for vector_double`[src]

### `impl Sync for vector_signed_long`[src]

### `impl Sync for vector_unsigned_long`[src]

### `impl Sync for v128`[src]

### `impl Sync for CpuidResult`[src]

### `impl Sync for __m128`[src]

### `impl Sync for __m128d`[src]

### `impl Sync for __m128i`[src]

### `impl Sync for __m256`[src]

### `impl Sync for __m256d`[src]

### `impl Sync for __m256i`[src]

### `impl Sync for __m512`[src]

### `impl Sync for __m512d`[src]

### `impl Sync for __m512i`[src]

### `impl Sync for TryFromSliceError`[src]

### `impl Sync for core::ascii::EscapeDefault`[src]

### `impl Sync for BorrowError`[src]

### `impl Sync for BorrowMutError`[src]

### `impl Sync for CharTryFromError`[src]

### `impl Sync for DecodeUtf16Error`[src]

### `impl Sync for core::char::EscapeDebug`[src]

### `impl Sync for core::char::EscapeDefault`[src]

### `impl Sync for core::char::EscapeUnicode`[src]

### `impl Sync for ParseCharError`[src]

### `impl Sync for ToLowercase`[src]

### `impl Sync for ToUppercase`[src]

### `impl Sync for Error`[src]

### `impl Sync for SipHasher`[src]

### `impl Sync for PhantomPinned`[src]

### `impl Sync for NonZeroI8`[src]

### `impl Sync for NonZeroI16`[src]

### `impl Sync for NonZeroI32`[src]

### `impl Sync for NonZeroI64`[src]

### `impl Sync for NonZeroI128`[src]

### `impl Sync for NonZeroIsize`[src]

### `impl Sync for NonZeroU8`[src]

### `impl Sync for NonZeroU16`[src]

### `impl Sync for NonZeroU32`[src]

### `impl Sync for NonZeroU64`[src]

### `impl Sync for NonZeroU128`[src]

### `impl Sync for NonZeroUsize`[src]

### `impl Sync for ParseFloatError`[src]

### `impl Sync for ParseIntError`[src]

### `impl Sync for TryFromIntError`[src]

### `impl Sync for RangeFull`[src]

### `impl Sync for NoneError`[src]

### `impl Sync for Utf8Lossy`[src]

### `impl Sync for ParseBoolError`[src]

### `impl Sync for Utf8Error`[src]

### `impl Sync for RawWakerVTable`[src]

### `impl Sync for Duration`[src]

### `impl<'a> !Sync for Arguments<'a>`[src]

### `impl<'a> !Sync for Formatter<'a>`[src]

### `impl<'a> !Sync for PanicInfo<'a>`[src]

### `impl<'a> Sync for Location<'a>`[src]

### `impl<'a> Sync for Utf8LossyChunk<'a>`[src]

### `impl<'a> Sync for Utf8LossyChunksIter<'a>`[src]

### `impl<'a> Sync for CharSearcher<'a>`[src]

### `impl<'a> Sync for Bytes<'a>`[src]

### `impl<'a> Sync for CharIndices<'a>`[src]

### `impl<'a> Sync for Chars<'a>`[src]

### `impl<'a> Sync for EncodeUtf16<'a>`[src]

### `impl<'a> Sync for core::str::EscapeDebug<'a>`[src]

### `impl<'a> Sync for core::str::EscapeDefault<'a>`[src]

### `impl<'a> Sync for core::str::EscapeUnicode<'a>`[src]

### `impl<'a> Sync for Lines<'a>`[src]

### `impl<'a> Sync for LinesAny<'a>`[src]

### `impl<'a> Sync for SplitAsciiWhitespace<'a>`[src]

### `impl<'a> Sync for SplitWhitespace<'a>`[src]

### `impl<'a> Sync for Context<'a>`[src]

### `impl<'a, 'b> !Sync for DebugList<'a, 'b>`[src]

### `impl<'a, 'b> !Sync for DebugMap<'a, 'b>`[src]

### `impl<'a, 'b> !Sync for DebugSet<'a, 'b>`[src]

### `impl<'a, 'b> !Sync for DebugStruct<'a, 'b>`[src]

### `impl<'a, 'b> !Sync for DebugTuple<'a, 'b>`[src]

### `impl<'a, 'b> Sync for CharSliceSearcher<'a, 'b>`[src]

### `impl<'a, 'b> Sync for StrSearcher<'a, 'b>`[src]

### `impl<'a, 'f> !Sync for VaList<'a, 'f>`[src]

### `impl<'a, A> Sync for core::option::Iter<'a, A> where
A: Sync,` [src]

### `impl<'a, A> Sync for core::option::IterMut<'a, A> where
A: Sync,` [src]

### `impl<'a, F> Sync for CharPredicateSearcher<'a, F> where
F: MultiCharEq + Sync,` [src]

### `impl<'a, P> Sync for MatchIndices<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for Matches<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for RMatchIndices<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for RMatches<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for core::str::RSplit<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for core::str::RSplitN<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for RSplitTerminator<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for core::str::Split<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for core::str::SplitN<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, P> Sync for SplitTerminator<'a, P> where
<P as Pattern<'a>>::Searcher: Sync,` [src]

### `impl<'a, T> Sync for core::result::Iter<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for core::result::IterMut<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for Chunks<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for ChunksExact<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for ChunksExactMut<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for ChunksMut<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for RChunks<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for RChunksExact<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for RChunksExactMut<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for RChunksMut<'a, T> where
T: Sync,` [src]

### `impl<'a, T> Sync for Windows<'a, T> where
T: Sync,` [src]

### `impl<'a, T, P> Sync for core::slice::RSplit<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for RSplitMut<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for core::slice::RSplitN<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for RSplitNMut<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for core::slice::Split<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for SplitInclusive<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for SplitInclusiveMut<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for SplitMut<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for core::slice::SplitN<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, P> Sync for SplitNMut<'a, T, P> where
P: Sync,
T: Sync,` [src]

### `impl<'a, T, const N: usize> !Sync for ArrayWindows<'a, T, N>`[src]

### `impl<'a, T, const N: usize> Sync for ArrayChunks<'a, T, N> where
T: Sync,` [src]

### `impl<'a, T, const N: usize> Sync for ArrayChunksMut<'a, T, N> where
T: Sync,` [src]

### `impl<'b, T> !Sync for Ref<'b, T>`[src]

### `impl<'b, T> !Sync for RefMut<'b, T>`[src]

### `impl<'f> !Sync for VaListImpl<'f>`[src]

### `impl<A> Sync for Repeat<A> where
A: Sync,` [src]

### `impl<A> Sync for core::option::IntoIter<A> where
A: Sync,` [src]

### `impl<A, B> Sync for Chain<A, B> where
A: Sync,
B: Sync,` [src]

### `impl<A, B> Sync for Zip<A, B> where
A: Sync,
B: Sync,` [src]

### `impl<B, C> Sync for ControlFlow<B, C> where
B: Sync,
C: Sync,` [src]

### `impl<F> Sync for PollFn<F> where
F: Sync,` [src]

### `impl<F> Sync for FromFn<F> where
F: Sync,` [src]

### `impl<F> Sync for OnceWith<F> where
F: Sync,` [src]

### `impl<F> Sync for RepeatWith<F> where
F: Sync,` [src]

### `impl<H> Sync for BuildHasherDefault<H> where
H: Sync,` [src]

### `impl<I> Sync for DecodeUtf16<I> where
I: Sync,` [src]

### `impl<I> Sync for Cloned<I> where
I: Sync,` [src]

### `impl<I> Sync for Copied<I> where
I: Sync,` [src]

### `impl<I> Sync for Cycle<I> where
I: Sync,` [src]

### `impl<I> Sync for Enumerate<I> where
I: Sync,` [src]

### `impl<I> Sync for Flatten<I> where
I: Sync,
<<I as Iterator>::Item as IntoIterator>::IntoIter: Sync,` [src]

### `impl<I> Sync for Fuse<I> where
I: Sync,` [src]

### `impl<I> Sync for Peekable<I> where
I: Sync,
<I as Iterator>::Item: Sync,` [src]

### `impl<I> Sync for Skip<I> where
I: Sync,` [src]

### `impl<I> Sync for StepBy<I> where
I: Sync,` [src]

### `impl<I> Sync for Take<I> where
I: Sync,` [src]

### `impl<I, F> Sync for FilterMap<I, F> where
F: Sync,
I: Sync,` [src]

### `impl<I, F> Sync for Inspect<I, F> where
F: Sync,
I: Sync,` [src]

### `impl<I, F> Sync for Map<I, F> where
F: Sync,
I: Sync,` [src]

### `impl<I, P> Sync for Filter<I, P> where
I: Sync,
P: Sync,` [src]

### `impl<I, P> Sync for MapWhile<I, P> where
I: Sync,
P: Sync,` [src]

### `impl<I, P> Sync for SkipWhile<I, P> where
I: Sync,
P: Sync,` [src]

### `impl<I, P> Sync for TakeWhile<I, P> where
I: Sync,
P: Sync,` [src]

### `impl<I, St, F> Sync for Scan<I, St, F> where
F: Sync,
I: Sync,
St: Sync,` [src]

### `impl<I, U, F> Sync for FlatMap<I, U, F> where
F: Sync,
I: Sync,
<U as IntoIterator>::IntoIter: Sync,` [src]

### `impl<Idx> Sync for Range<Idx> where
Idx: Sync,` [src]

### `impl<Idx> Sync for RangeFrom<Idx> where
Idx: Sync,` [src]

### `impl<Idx> Sync for RangeInclusive<Idx> where
Idx: Sync,` [src]

### `impl<Idx> Sync for RangeTo<Idx> where
Idx: Sync,` [src]

### `impl<Idx> Sync for RangeToInclusive<Idx> where
Idx: Sync,` [src]

### `impl<P> Sync for Pin<P> where
P: Sync,` [src]

### `impl<T> !Sync for OnceCell<T>`[src]

### `impl<T> Sync for Bound<T> where
T: Sync,` [src]

### `impl<T> Sync for Option<T> where
T: Sync,` [src]

### `impl<T> Sync for Poll<T> where
T: Sync,` [src]

### `impl<T> Sync for Reverse<T> where
T: Sync,` [src]

### `impl<T> Sync for Pending<T> where
T: Sync,` [src]

### `impl<T> Sync for Ready<T> where
T: Sync,` [src]

### `impl<T> Sync for Once<T> where
T: Sync,` [src]

### `impl<T> Sync for Rev<T> where
T: Sync,` [src]

### `impl<T> Sync for Discriminant<T> where
<T as DiscriminantKind>::Discriminant: Sync,` [src]

### `impl<T> Sync for Wrapping<T> where
T: Sync,` [src]

### `impl<T> Sync for core::result::IntoIter<T> where
T: Sync,` [src]

### `impl<T> Sync for MaybeUninit<T> where
T: Sync,` [src]

### `impl<T, E> Sync for Result<T, E> where
E: Sync,
T: Sync,` [src]

### `impl<T, F> Sync for Successors<T, F> where
F: Sync,
T: Sync,` [src]

### `impl<T, F = fn() -> T> !Sync for Lazy<T, F>`[src]

### `impl<T, const N: usize> Sync for core::array::IntoIter<T, N> where
T: Sync,` [src]

### `impl<T: ?Sized> Sync for PhantomData<T> where
T: Sync,` [src]

### `impl<T: ?Sized> Sync for ManuallyDrop<T> where
T: Sync,` [src]

### `impl<Y, R> Sync for GeneratorState<Y, R> where
R: Sync,
Y: Sync,` [src]

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