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

    pub unsafe auto trait Sync { }

Expand description

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

[src]

### impl Sync for AtomicBool

1.34.0[src]

### impl Sync for AtomicI8

1.34.0[src]

### impl Sync for AtomicI16

1.34.0[src]

### impl Sync for AtomicI32

1.34.0[src]

### impl Sync for AtomicI64

[src]

### impl Sync for AtomicIsize

1.34.0[src]

### impl Sync for AtomicU8

1.34.0[src]

### impl Sync for AtomicU16

1.34.0[src]

### impl Sync for AtomicU32

1.34.0[src]

### impl Sync for AtomicU64

[src]

### impl Sync for AtomicUsize

1.36.0[src]

### impl Sync for Waker

[src]

### impl<Dyn: ?Sized> Sync for DynMetadata<Dyn>

1.42.0[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>

1.25.0[src]

### impl<T: ?Sized> !Sync for NonNull<T>

## Auto implementors

### 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 AllocError

### impl Sync for Layout

### impl Sync for LayoutError

### 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 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 int16x2_t

### impl Sync for uint16x2_t

### impl Sync for APSR

### impl Sync for SY

### impl Sync for float32x2_t

### impl Sync for float32x4_t

### impl Sync for int8x4_t

### impl Sync for int8x8_t

### impl Sync for int8x8x2_t

### impl Sync for int8x8x3_t

### impl Sync for int8x8x4_t

### impl Sync for int8x16_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 poly8x8_t

### impl Sync for poly8x8x2_t

### impl Sync for poly8x8x3_t

### impl Sync for poly8x8x4_t

### impl Sync for poly8x16_t

### impl Sync for poly16x4_t

### impl Sync for poly16x8_t

### impl Sync for poly64x1_t

### impl Sync for poly64x2_t

### impl Sync for uint8x4_t

### impl Sync for uint8x8_t

### impl Sync for uint8x8x2_t

### impl Sync for uint8x8x3_t

### impl Sync for uint8x8x4_t

### impl Sync for uint8x16_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 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 __m128bh

### impl Sync for __m128d

### impl Sync for __m128i

### impl Sync for __m256

### impl Sync for __m256bh

### impl Sync for __m256d

### impl Sync for __m256i

### impl Sync for __m512

### impl Sync for __m512bh

### impl Sync for __m512d

### impl Sync for __m512i

### 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 Error

### impl Sync for SipHasher

### impl Sync for NonZeroI8

### impl Sync for NonZeroI16

### impl Sync for NonZeroI32

### impl Sync for NonZeroI64

### impl Sync for NonZeroI128

### impl Sync for NonZeroIsize

### impl Sync for NonZeroU8

### impl Sync for NonZeroU16

### impl Sync for NonZeroU32

### impl Sync for NonZeroU64

### impl Sync for NonZeroU128

### impl Sync for NonZeroUsize

### impl Sync for ParseFloatError

### impl Sync for ParseIntError

### impl Sync for TryFromIntError

### impl Sync for RangeFull

### impl Sync for Utf8Lossy

### impl Sync for ParseBoolError

### impl Sync for Utf8Error

### impl Sync for RawWakerVTable

### impl Sync for Duration

### impl Sync for FromSecsError

### impl Sync for PhantomPinned

### 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 EscapeAscii<'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, 'f> !Sync for VaList<'a, 'f>

### 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: 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::SplitInclusive<'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 GroupBy<'a, T, P> where
P: Sync,
T: Sync,

### impl<'a, T, P> Sync for GroupByMut<'a, T, P> where
P: Sync,
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 core::slice::SplitInclusive<'a, T, P> where
P: Sync,
T: Sync,

### impl<'a, T, P> Sync for SplitInclusiveMut<'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<'a, T, const N: usize> !Sync for ArrayWindows<'a, T, N>

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

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

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

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

### impl<'f> !Sync for VaListImpl<'f>

### 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<B, C> Sync for ControlFlow<B, C> where
B: Sync,
C: Sync,

### impl<F> Sync for PollFn<F> where
F: 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 Intersperse<I> where
I: Sync,
<I as Iterator>::Item: 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> Sync for FromIter<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, G> Sync for IntersperseWith<I, G> where
G: Sync,
I: Sync,
<I as Iterator>::Item: Sync,

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

### impl<I, P> Sync for MapWhile<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 OnceCell<T>

### 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 Pending<T> where
T: Sync,

### impl<T> Sync for Ready<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 Saturating<T> where
T: Sync,

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

### impl<T> Sync for AssertUnwindSafe<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, F = fn() -> T> !Sync for Lazy<T, F>

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

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

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

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