Trait std::marker::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
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
.
Implementations on Foreign Types
impl Sync for Argument
impl Sync for FormatSpec
impl Sync for Alignment
impl Sync for Count
Implementors
impl !Sync for Args
impl !Sync for ArgsOs
impl Sync for AtomicBool
impl Sync for AtomicI8
impl Sync for AtomicI16
impl Sync for AtomicI32
impl Sync for AtomicI64
impl Sync for AtomicIsize
impl Sync for AtomicU8
impl Sync for AtomicU16
impl Sync for AtomicU32
impl Sync for AtomicU64
impl Sync for AtomicUsize
impl Sync for std::sync::Once
impl Sync for Waker
impl<'_> Sync for std::string::Drain<'_>
impl<'_, T, A> Sync for std::collections::vec_deque::Drain<'_, T, A> where
T: Sync,
A: Allocator + Sync,
impl<'a> Sync for IoSlice<'a>
impl<'a> Sync for IoSliceMut<'a>
NonNull
pointers are not Sync
because the data they reference may be aliased.
impl<T> !Sync for Receiver<T>
impl<T> !Sync for Sender<T>
impl<T> Sync for std::iter::Empty<T>
impl<T> Sync for AtomicPtr<T>
impl<T> Sync for JoinHandle<T>
impl<T, F: Send> Sync for SyncLazy<T, F> where
SyncOnceCell<T>: Sync,
impl<T: Sync + Send> Sync for SyncOnceCell<T>
impl<T: ?Sized + Send + Sync> Sync for RwLock<T>
impl<T: ?Sized + Send> Sync for Mutex<T>
impl<T: ?Sized + Sync> Sync for MutexGuard<'_, T>
impl<T: ?Sized + Sync> Sync for RwLockReadGuard<'_, T>
impl<T: ?Sized + Sync> Sync for RwLockWriteGuard<'_, T>
Auto implementors
impl !Sync for Vars
impl !Sync for VarsOs
impl !Sync for OnceState
impl !Sync for RawWaker
impl Sync for BacktraceStatus
impl Sync for std::cmp::Ordering
impl Sync for TryReserveErrorKind
impl Sync for Infallible
impl Sync for VarError
impl Sync for c_void
impl Sync for std::fmt::Alignment
impl Sync for ErrorKind
impl Sync for SeekFrom
impl Sync for IpAddr
impl Sync for Ipv6MulticastScope
impl Sync for Shutdown
impl Sync for std::net::SocketAddr
impl Sync for FpCategory
impl Sync for IntErrorKind
impl Sync for AncillaryError
impl Sync for SearchStep
impl Sync for std::sync::atomic::Ordering
impl Sync for RecvTimeoutError
impl Sync for TryRecvError
impl Sync for bool
impl Sync for char
impl Sync for f32
impl Sync for f64
impl Sync for i8
impl Sync for i16
impl Sync for i32
impl Sync for i64
impl Sync for i128
impl Sync for isize
impl Sync for [u8]
impl Sync for str
impl Sync for u8
impl Sync for u16
impl Sync for u32
impl Sync for u64
impl Sync for u128
impl Sync for usize
impl Sync for AllocError
impl Sync for Global
impl Sync for Layout
impl Sync for LayoutError
impl Sync for System
impl Sync for TypeId
impl Sync for TryFromSliceError
impl Sync for std::ascii::EscapeDefault
impl Sync for Backtrace
impl Sync for BacktraceFrame
impl Sync for BorrowError
impl Sync for BorrowMutError
impl Sync for CharTryFromError
impl Sync for DecodeUtf16Error
impl Sync for std::char::EscapeDebug
impl Sync for std::char::EscapeDefault
impl Sync for std::char::EscapeUnicode
impl Sync for ParseCharError
impl Sync for ToLowercase
impl Sync for ToUppercase
impl Sync for DefaultHasher
impl Sync for RandomState
impl Sync for TryReserveError
impl Sync for JoinPathsError
impl Sync for CStr
impl Sync for CString
impl Sync for FromBytesWithNulError
impl Sync for FromVecWithNulError
impl Sync for IntoStringError
impl Sync for NulError
impl Sync for OsStr
impl Sync for OsString
impl Sync for std::fmt::Error
impl Sync for DirBuilder
impl Sync for DirEntry
impl Sync for File
impl Sync for FileType
impl Sync for Metadata
impl Sync for OpenOptions
impl Sync for Permissions
impl Sync for ReadDir
impl Sync for SipHasher
impl Sync for std::io::Empty
impl Sync for std::io::Error
impl Sync for Initializer
impl Sync for std::io::Repeat
impl Sync for Sink
impl Sync for Stderr
impl Sync for Stdin
impl Sync for Stdout
impl Sync for WriterPanicked
impl Sync for AddrParseError
impl Sync for Ipv4Addr
impl Sync for Ipv6Addr
impl Sync for SocketAddrV4
impl Sync for SocketAddrV6
impl Sync for TcpListener
impl Sync for TcpStream
impl Sync for UdpSocket
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 PidFd
impl Sync for stat
impl Sync for OwnedFd
impl Sync for std::os::unix::net::SocketAddr
impl Sync for SocketCred
impl Sync for UCred
impl Sync for UnixDatagram
impl Sync for UnixListener
impl Sync for UnixStream
impl Sync for OwnedSocket
impl Sync for Path
impl Sync for PathBuf
impl Sync for StripPrefixError
impl Sync for Child
impl Sync for ChildStderr
impl Sync for ChildStdin
impl Sync for ChildStdout
impl Sync for Command
impl Sync for ExitCode
impl Sync for ExitStatus
impl Sync for ExitStatusError
impl Sync for Output
impl Sync for Stdio
impl Sync for ParseBoolError
impl Sync for Utf8Error
impl Sync for FromUtf8Error
impl Sync for FromUtf16Error
impl Sync for String
impl Sync for RecvError
impl Sync for Barrier
impl Sync for BarrierWaitResult
impl Sync for Condvar
impl Sync for WaitTimeoutResult
impl Sync for RawWakerVTable
impl Sync for AccessError
impl Sync for Builder
impl Sync for Thread
impl Sync for ThreadId
impl Sync for Duration
impl Sync for Instant
impl Sync for SystemTime
impl Sync for SystemTimeError
impl Sync for PhantomPinned
impl<'a> !Sync for std::error::Chain<'a>
impl<'a> !Sync for Arguments<'a>
impl<'a> !Sync for Formatter<'a>
impl<'a> !Sync for PanicInfo<'a>
impl<'a> Sync for AncillaryData<'a>
impl<'a> Sync for Component<'a>
impl<'a> Sync for Prefix<'a>
impl<'a> Sync for SplitPaths<'a>
impl<'a> Sync for StderrLock<'a>
impl<'a> Sync for StdinLock<'a>
impl<'a> Sync for StdoutLock<'a>
impl<'a> Sync for std::net::Incoming<'a>
impl<'a> Sync for std::os::unix::net::Incoming<'a>
impl<'a> Sync for Messages<'a>
impl<'a> Sync for ScmCredentials<'a>
impl<'a> Sync for ScmRights<'a>
impl<'a> Sync for SocketAncillary<'a>
impl<'a> Sync for EncodeWide<'a>
impl<'a> Sync for Location<'a>
impl<'a> Sync for Ancestors<'a>
impl<'a> Sync for Components<'a>
impl<'a> Sync for Display<'a>
impl<'a> Sync for std::path::Iter<'a>
impl<'a> Sync for PrefixComponent<'a>
impl<'a> Sync for CommandArgs<'a>
impl<'a> Sync for CommandEnvs<'a>
impl<'a> Sync for CharSearcher<'a>
impl<'a> Sync for std::str::Bytes<'a>
impl<'a> Sync for CharIndices<'a>
impl<'a> Sync for Chars<'a>
impl<'a> Sync for EncodeUtf16<'a>
impl<'a> Sync for std::str::EscapeDebug<'a>
impl<'a> Sync for std::str::EscapeDefault<'a>
impl<'a> Sync for std::str::EscapeUnicode<'a>
impl<'a> Sync for std::str::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 std::option::Iter<'a, A> where
A: Sync,
impl<'a, A> Sync for std::option::IterMut<'a, A> where
A: Sync,
impl<'a, F> Sync for CharPredicateSearcher<'a, F> where
F: Sync,
impl<'a, K> Sync for std::collections::hash_set::Drain<'a, K> where
K: Sync,
impl<'a, K> Sync for std::collections::hash_set::Iter<'a, K> where
K: Sync,
impl<'a, K, V> Sync for std::collections::btree_map::OccupiedEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for std::collections::btree_map::OccupiedError<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V, F> Sync for std::collections::btree_map::DrainFilter<'a, K, V, F> where
F: Sync,
K: Sync,
V: Sync,
impl<'a, K, V, F> Sync for std::collections::hash_map::DrainFilter<'a, K, V, F> where
F: Sync,
K: Sync,
V: Sync,
impl<'a, T> !Sync for std::sync::mpsc::Iter<'a, T>
impl<'a, T> !Sync for TryIter<'a, T>
impl<'a, T> Sync for std::collections::binary_heap::Drain<'a, T> where
T: Sync,
impl<'a, T> Sync for DrainSorted<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::binary_heap::Iter<'a, T> where
T: Sync,
impl<'a, T> Sync for PeekMut<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::btree_set::Difference<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::btree_set::Intersection<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::btree_set::Iter<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::btree_set::Range<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::btree_set::SymmetricDifference<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::btree_set::Union<'a, T> where
T: Sync,
impl<'a, T> Sync for std::collections::vec_deque::Iter<'a, T> where
T: Sync,
impl<'a, T> Sync for std::result::Iter<'a, T> where
T: Sync,
impl<'a, T> Sync for 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 std::collections::linked_list::DrainFilter<'a, T, F>
impl<'a, T, S> Sync for std::collections::hash_set::SymmetricDifference<'a, T, S> where
S: 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<'fd> Sync for BorrowedFd<'fd>
impl<'socket> Sync for BorrowedSocket<'socket>
impl<A> Sync for std::iter::Repeat<A> where
A: Sync,
impl<A> Sync for std::option::IntoIter<A> where
A: Sync,
impl<B> Sync for std::io::Lines<B> where
B: Sync,
impl<B> Sync for std::io::Split<B> where
B: 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 Fuse<I> where
I: Sync,
impl<I> Sync for Skip<I> where
I: Sync,
impl<I> Sync for StepBy<I> where
I: Sync,
impl<I> Sync for std::iter::Take<I> where
I: Sync,
impl<I> Sync for FromIter<I> where
I: 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 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> Sync for std::collections::hash_set::IntoIter<K> where
K: Sync,
impl<P> Sync for Pin<P> where
P: Sync,
impl<R> Sync for BufReader<R> where
R: Sync,
impl<R> Sync for std::io::Bytes<R> where
R: Sync,
impl<T> !Sync for OnceCell<T>
impl<T> !Sync for std::sync::mpsc::IntoIter<T>
impl<T> Sync for Bound<T> where
T: Sync,
impl<T> Sync for Option<T> where
T: Sync,
impl<T> Sync for TryLockError<T> where
T: Sync,
impl<T> Sync for TrySendError<T> where
T: Sync,
impl<T> Sync for Poll<T> where
T: Sync,
impl<T> Sync for [T] where
T: Sync,
impl<T> Sync for Reverse<T> where
T: Sync,
impl<T> Sync for std::collections::binary_heap::IntoIter<T> where
T: Sync,
impl<T> Sync for IntoIterSorted<T> where
T: Sync,
impl<T> Sync for std::collections::btree_set::IntoIter<T> where
T: Sync,
impl<T> Sync for std::collections::linked_list::IntoIter<T> where
T: Sync,
impl<T> Sync for BTreeSet<T> where
T: Sync,
impl<T> Sync for BinaryHeap<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 std::io::Cursor<T> where
T: Sync,
impl<T> Sync for std::io::Take<T> where
T: Sync,
impl<T> Sync for 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 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 std::result::IntoIter<T> where
T: Sync,
impl<T> Sync for SendError<T> where
T: Sync,
impl<T> Sync for SyncSender<T> where
T: Send,
impl<T> Sync for PoisonError<T> where
T: Sync,
impl<T> Sync for LocalKey<T>
impl<T> Sync for MaybeUninit<T> where
T: Sync,
impl<T, F = fn() -> T> !Sync for Lazy<T, F>
impl<T, const N: usize> Sync for [T; N] where
T: Sync,
impl<T, const N: usize> Sync for std::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<W> Sync for BufWriter<W> where
W: Sync,
impl<W> Sync for IntoInnerError<W> where
W: Sync,
impl<W> Sync for LineWriter<W> where
W: Sync,
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/marker/trait.Sync.html