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 LocalWaker
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impl Sync for AtomicBool
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impl Sync for AtomicI16
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impl Sync for AtomicI32
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impl Sync for AtomicI64
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impl Sync for AtomicI8
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impl Sync for AtomicIsize
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impl Sync for AtomicU16
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impl Sync for AtomicU32
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impl Sync for AtomicU64
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impl Sync for AtomicU8
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impl Sync for AtomicUsize
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impl Sync for Waker
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impl<'a, T: Sync> Sync for core::slice::Iter<'a, T>
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impl<'a, T: Sync> Sync for core::slice::IterMut<'a, T>
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impl<T> Sync for AtomicPtr<T>
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impl<T: ?Sized> !Sync for *const T
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impl<T: ?Sized> !Sync for *mut T
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impl<T: ?Sized> !Sync for Cell<T>
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impl<T: ?Sized> !Sync for RefCell<T>
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impl<T: ?Sized> !Sync for UnsafeCell<T>
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impl<T: ?Sized> !Sync for NonNull<T>
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NonNull pointers are not Sync because the data they reference may be aliased.

Auto implementors

impl !Sync for Excess

impl !Sync for TraitObject

impl !Sync for SpawnLocalObjError

impl !Sync for SpawnObjError

impl Sync for core::cmp::Ordering

impl Sync for c_void

impl Sync for Alignment

impl Sync for FpCategory

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 float32x2_t

impl Sync for float32x4_t

impl Sync for int16x2_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 int8x4_t

impl Sync for int8x8_t

impl Sync for poly16x4_t

impl Sync for poly16x8_t

impl Sync for poly8x16_t

impl Sync for poly8x8_t

impl Sync for uint16x2_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 uint8x4_t

impl Sync for uint8x8_t

impl Sync for i8x16

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 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 __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 EscapeDebug

impl Sync for core::char::EscapeDefault

impl Sync for 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 Pinned

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 SpawnErrorKind

impl Sync for Duration

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

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

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

impl<'a> !Sync for Context<'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 Lines<'a>

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

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

impl<'a> Sync for SplitWhitespace<'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: 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 FutureObj<'a, T>

impl<'a, T> !Sync for LocalFutureObj<'a, T>

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 ChunksMut<'a, T> where
    T: Sync

impl<'a, T> Sync for ExactChunks<'a, T> where
    T: Sync

impl<'a, T> Sync for ExactChunksMut<'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<'a, T: ?Sized> Sync for PinMut<'a, T> where
    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 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 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<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, E> Sync for Result<T, E> where
    E: 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