Trait alloc::prelude::v1::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.

Implementations on Foreign Types

impl Sync for Decoded

impl Sync for FullDecoded

impl<'a> Sync for Part<'a>

impl<'a> Sync for Formatted<'a>

impl Sync for Sign

impl Sync for Unpacked

impl Sync for Sign

impl<'a> Sync for Decimal<'a>

impl<'a> Sync for ParseResult<'a>

impl Sync for ParseFloatError

impl Sync for Big32x40

impl Sync for Big8x3

impl Sync for Argument

impl Sync for FormatSpec

impl Sync for Alignment

impl Sync for Count

impl Sync for Position

impl<T> !Sync for Sender<T>

impl<T> Sync for RwLock<T> where     T: Send + Sync + ?Sized,

impl !Sync for Args

impl<T> Sync for Key<T>

impl<T> Sync for Mutex<T> where     T: Send + ?Sized,

impl Sync for Once

impl<'a, T> Sync for RwLockWriteGuard<'a, T> where     T: Sync + ?Sized,

impl !Sync for ArgsOs

impl<'a, T> Sync for RwLockReadGuard<'a, T> where     T: Sync + ?Sized,

impl<'a, T> Sync for MutexGuard<'a, T> where     T: Sync + ?Sized,

impl<T> !Sync for Receiver<T>

impl<T> Sync for JoinHandle<T>

impl<T> !Sync for *mut T where     T: ?Sized,

impl<T> !Sync for *const T where     T: ?Sized,

impl<T> !Sync for Rc<T> where     T: ?Sized,

impl<'a> Sync for Drain<'a>

impl<T> Sync for IntoIter<T> where     T: Sync,

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

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

impl<T> !Sync for Weak<T> where     T: ?Sized,

impl<T> Sync for LinkedList<T> where     T: Sync,

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

impl<T> Sync for Weak<T> where     T: Send + Sync + ?Sized,

impl<T> Sync for Arc<T> where     T: Send + Sync + ?Sized,

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

impl Sync for isize

impl Sync for i8

impl Sync for i16

impl Sync for i32

impl Sync for i64

impl Sync for i128

impl Sync for usize

impl Sync for u8

impl Sync for u16

impl Sync for u32

impl Sync for u64

impl Sync for u128

impl Sync for f32

impl Sync for f64

impl Sync for f32

impl Sync for f64

impl Sync for char

impl Sync for str

impl Sync for str

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Implementors

impl !Sync for LocalWaker

impl Sync for Waker

impl Sync for AtomicUsize

impl Sync for AtomicBool

impl Sync for AtomicIsize

impl Sync for AtomicI16

impl Sync for AtomicI32

impl Sync for AtomicI64

impl Sync for AtomicI8

impl Sync for AtomicU16

impl Sync for AtomicU32

impl Sync for AtomicU64

impl Sync for AtomicU8

impl<'_, T> Sync for alloc::slice::Iter<'_, T> where     T: Sync,

impl<'_, T> Sync for alloc::slice::IterMut<'_, T> where     T: Sync,

impl<T> !Sync for Cell<T> where     T: ?Sized,

impl<T> !Sync for RefCell<T> where     T: ?Sized,

impl<T> !Sync for UnsafeCell<T> where     T: ?Sized,

impl<T> !Sync for NonNull<T> where     T: ?Sized,

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

impl<T> Sync for AtomicPtr<T>

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Auto implementors

impl !Sync for TraitObject

impl !Sync for Excess

impl Sync for SearchStep

impl Sync for ParseBoolError

impl Sync for NonZeroUsize

impl Sync for FpCategory

impl Sync for TryFromIntError

impl Sync for ParseIntError

impl Sync for IntErrorKind

impl Sync for PhantomPinned

impl Sync for RangeFull

impl Sync for alloc::cmp::Ordering

impl Sync for TypeId

impl Sync for TryFromSliceError

impl Sync for alloc::ascii::EscapeDefault

impl Sync for alloc::sync::atomic::Ordering

impl Sync for BorrowError

impl Sync for BorrowMutError

impl Sync for EscapeUnicode

impl Sync for alloc::char::EscapeDefault

impl Sync for EscapeDebug

impl Sync for ToLowercase

impl Sync for ToUppercase

impl Sync for UnicodeVersion

impl Sync for ParseCharError

impl Sync for CharTryFromError

impl Sync for NoneError

impl Sync for c_void

impl Sync for SipHasher

impl Sync for alloc::fmt::Alignment

impl Sync for Error

impl Sync for Duration

impl Sync for Layout

impl Sync for LayoutErr

impl Sync for AllocErr

impl Sync for CannotReallocInPlace

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 DecodeUtf16Error

impl Sync for NonZeroU128

impl Sync for NonZeroU16

impl Sync for NonZeroU32

impl Sync for NonZeroU64

impl Sync for NonZeroU8

impl Sync for Utf8Lossy

impl Sync for Utf8Error

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

impl<'a, A> Sync for alloc::option::Iter<'a, A> where     A: Sync,

impl<'a, A> Sync for alloc::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 alloc::str::RSplit<'a, P> where     <P as Pattern<'a>>::Searcher: Sync,

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

impl<'a, P> Sync for alloc::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 alloc::result::Iter<'a, T> where     T: Sync,

impl<'a, T> Sync for alloc::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 alloc::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 alloc::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 alloc::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 alloc::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 alloc::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 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<St, F> Sync for Unfold<St, F> where     F: Sync,     St: Sync,

impl<T> Sync for Discriminant<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 Empty<T> where     T: Sync,

impl<T> Sync for alloc::iter::Once<T> where     T: Sync,

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

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

impl<T> Sync for alloc::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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