# 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::Cell` and `cell::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::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 AtomicI16`[src]

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

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

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

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

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

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

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

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

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

### `impl Sync for Waker`[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 Excess`

### `impl !Sync for TraitObject`

### `impl !Sync for RawWaker`

### `impl Sync for core::cmp::Ordering`

### `impl Sync for Infallible`

### `impl Sync for c_void`

### `impl Sync for Alignment`

### `impl Sync for FpCategory`

### `impl Sync for IntErrorKind`

### `impl Sync for SearchStep`

### `impl Sync for core::sync::atomic::Ordering`

### `impl Sync for AllocErr`

### `impl Sync for CannotReallocInPlace`

### `impl Sync for Layout`

### `impl Sync for LayoutErr`

### `impl Sync for TypeId`

### `impl Sync for float64x1_t`

### `impl Sync for float64x2_t`

### `impl Sync for int8x16x2_t`

### `impl Sync for int8x16x3_t`

### `impl Sync for int8x16x4_t`

### `impl Sync for poly64x1_t`

### `impl Sync for poly64x2_t`

### `impl Sync for poly8x16x2_t`

### `impl Sync for poly8x16x3_t`

### `impl Sync for poly8x16x4_t`

### `impl Sync for uint8x16x2_t`

### `impl Sync for uint8x16x3_t`

### `impl Sync for uint8x16x4_t`

### `impl Sync for APSR`

### `impl Sync for SY`

### `impl Sync for float32x2_t`

### `impl Sync for float32x4_t`

### `impl Sync for int16x4_t`

### `impl Sync for int16x8_t`

### `impl Sync for int32x2_t`

### `impl Sync for int32x4_t`

### `impl Sync for int64x1_t`

### `impl Sync for int64x2_t`

### `impl Sync for int8x16_t`

### `impl Sync for int8x8_t`

### `impl Sync for int8x8x2_t`

### `impl Sync for int8x8x3_t`

### `impl Sync for int8x8x4_t`

### `impl Sync for poly16x4_t`

### `impl Sync for poly16x8_t`

### `impl Sync for poly8x16_t`

### `impl Sync for poly8x8_t`

### `impl Sync for poly8x8x2_t`

### `impl Sync for poly8x8x3_t`

### `impl Sync for poly8x8x4_t`

### `impl Sync for uint16x4_t`

### `impl Sync for uint16x8_t`

### `impl Sync for uint32x2_t`

### `impl Sync for uint32x4_t`

### `impl Sync for uint64x1_t`

### `impl Sync for uint64x2_t`

### `impl Sync for uint8x16_t`

### `impl Sync for uint8x8_t`

### `impl Sync for uint8x8x2_t`

### `impl Sync for uint8x8x3_t`

### `impl Sync for uint8x8x4_t`

### `impl Sync for v16i8`

### `impl Sync for v16u8`

### `impl Sync for v2f64`

### `impl Sync for v2i64`

### `impl Sync for v2u64`

### `impl Sync for v4f32`

### `impl Sync for v4i32`

### `impl Sync for v4u32`

### `impl Sync for v8i16`

### `impl Sync for v8u16`

### `impl Sync for vector_bool_long`

### `impl Sync for vector_double`

### `impl Sync for vector_signed_long`

### `impl Sync for vector_unsigned_long`

### `impl Sync for v128`

### `impl Sync for CpuidResult`

### `impl Sync for __m128`

### `impl Sync for __m128d`

### `impl Sync for __m128i`

### `impl Sync for __m256`

### `impl Sync for __m256d`

### `impl Sync for __m256i`

### `impl Sync for __m512`

### `impl Sync for __m512d`

### `impl Sync for __m512i`

### `impl Sync for __m64`

### `impl Sync for TryFromSliceError`

### `impl Sync for core::ascii::EscapeDefault`

### `impl Sync for BorrowError`

### `impl Sync for BorrowMutError`

### `impl Sync for CharTryFromError`

### `impl Sync for DecodeUtf16Error`

### `impl Sync for core::char::EscapeDebug`

### `impl Sync for core::char::EscapeDefault`

### `impl Sync for core::char::EscapeUnicode`

### `impl Sync for ParseCharError`

### `impl Sync for ToLowercase`

### `impl Sync for ToUppercase`

### `impl Sync for UnicodeVersion`

### `impl Sync for Error`

### `impl Sync for SipHasher`

### `impl Sync for PhantomPinned`

### `impl Sync for NonZeroI128`

### `impl Sync for NonZeroI16`

### `impl Sync for NonZeroI32`

### `impl Sync for NonZeroI64`

### `impl Sync for NonZeroI8`

### `impl Sync for NonZeroIsize`

### `impl Sync for NonZeroU128`

### `impl Sync for NonZeroU16`

### `impl Sync for NonZeroU32`

### `impl Sync for NonZeroU64`

### `impl Sync for NonZeroU8`

### `impl Sync for NonZeroUsize`

### `impl Sync for ParseFloatError`

### `impl Sync for ParseIntError`

### `impl Sync for TryFromIntError`

### `impl Sync for RangeFull`

### `impl Sync for NoneError`

### `impl Sync for Utf8Lossy`

### `impl Sync for ParseBoolError`

### `impl Sync for Utf8Error`

### `impl Sync for RawWakerVTable`

### `impl Sync for Duration`

### `impl<'a> !Sync for VaList<'a>`

### `impl<'a> !Sync for Arguments<'a>`

### `impl<'a> !Sync for Formatter<'a>`

### `impl<'a> !Sync for PanicInfo<'a>`

### `impl<'a> Sync for Location<'a>`

### `impl<'a> Sync for Utf8LossyChunk<'a>`

### `impl<'a> Sync for Utf8LossyChunksIter<'a>`

### `impl<'a> Sync for CharSearcher<'a>`

### `impl<'a> Sync for Bytes<'a>`

### `impl<'a> Sync for CharIndices<'a>`

### `impl<'a> Sync for Chars<'a>`

### `impl<'a> Sync for EncodeUtf16<'a>`

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

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

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

### `impl<'a> Sync for Lines<'a>`

### `impl<'a> Sync for LinesAny<'a>`

### `impl<'a> Sync for SplitAsciiWhitespace<'a>`

### `impl<'a> Sync for SplitWhitespace<'a>`

### `impl<'a> Sync for Context<'a>`

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

### `impl<T> Sync for Empty<T> where
T: Sync,`

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

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

### `impl<T> Sync for Discriminant<T>`

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

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

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

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

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

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

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

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

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