Trait sr_std::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.

Implementations on Foreign Types

impl Sync for Argument

impl Sync for FormatSpec

impl Sync for Alignment

impl Sync for Count

impl Sync for Position

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

impl !Sync for ArgsOs

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

impl Sync for Once

impl<T> !Sync for Sender<T>

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

impl<T> Sync for JoinHandle<T>

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

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

impl !Sync for Args

impl<T> Sync for Key<T>

impl<T> !Sync for Receiver<T>

impl Sync for AtomicU8

impl Sync for AtomicI32

impl Sync for AtomicI8

impl Sync for AtomicBool

impl Sync for AtomicUsize

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

impl Sync for Waker

impl Sync for AtomicI64

impl Sync for AtomicI16

impl Sync for AtomicU64

impl Sync for AtomicU32

impl Sync for AtomicIsize

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

impl Sync for AtomicU16

impl<T> Sync for AtomicPtr<T>

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

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

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

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

impl<'_> Sync for Drain<'_>

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

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

impl<'_, K, V, S> Sync for OccupiedEntry<'_, K, V, S> where
    K: Sync,
    S: Sync,
    V: Sync, 

impl<'_, K, V> Sync for RustcOccupiedEntry<'_, K, V> where
    K: Sync,
    V: 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 bool

impl Sync for char

impl Sync for str

impl<T> Sync for [T] where
    T: Sync, 

impl Sync for [u8]

Loading content...

Implementors

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

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

impl<'_, T> Sync for sr_std::vec::Drain<'_, 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 Rc<T> where
    T: ?Sized, 

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

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

Loading content...

Auto implementors

impl Sync for Ordering

impl Sync for Infallible

impl Sync for sr_std::fmt::Alignment

impl Sync for FpCategory

impl Sync for IntErrorKind

impl Sync for BorrowError

impl Sync for BorrowMutError

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

impl<'a> !Sync for Formatter<'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: ?Sized> Sync for Cow<'a, B> where
    B: Sync,
    <B as ToOwned>::Owned: Sync, 

impl<'a, I> Sync for Splice<'a, I> where
    I: Sync,
    <I as Iterator>::Item: Sync, 

impl<'a, K, V> Sync for Entry<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for sr_std::collections::btree_map::Iter<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for sr_std::collections::btree_map::IterMut<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for Keys<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for sr_std::collections::btree_map::OccupiedEntry<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for sr_std::collections::btree_map::Range<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for RangeMut<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for VacantEntry<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for Values<'a, K, V> where
    K: Sync,
    V: Sync, 

impl<'a, K, V> Sync for ValuesMut<'a, K, V> where
    K: Sync,
    V: Sync, 

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

impl<'a, T> Sync for sr_std::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, F> Sync for DrainFilter<'a, T, F> where
    F: Sync,
    T: Sync, 

impl<'a, T, P> Sync for 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 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 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 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, 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 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 sr_std::ops::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<K, V> Sync for BTreeMap<K, V> where
    K: Sync,
    V: Sync, 

impl<K, V> Sync for sr_std::collections::btree_map::IntoIter<K, V> where
    K: Sync,
    V: Sync, 

impl<T> Sync for Bound<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 sr_std::iter::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 Vec<T> where
    T: Sync, 

impl<T> Sync for sr_std::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<T: ?Sized> Sync for Box<T> where
    T: Sync, 

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

Loading content...