Trait ockam_core::lib::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
.
Implementations on Foreign Types
impl Sync for AccessError
impl Sync for EscapeDefault
impl Sync for BacktraceStatus
impl Sync for BacktraceFrame
impl<'a, K, V, F> Sync for DrainFilter<'a, K, V, F> where
F: Sync,
K: Sync,
V: Sync,
impl<K, V> Sync for IntoValues<K, V> where
K: Sync,
V: Sync,
impl<'a, K, V, S> Sync for RawEntryBuilderMut<'a, K, V, S> where
K: Sync,
S: Sync,
V: Sync,
impl<'a, K, V, S> Sync for RawEntryMut<'a, K, V, S> where
K: Sync,
S: Sync,
V: Sync,
impl<'a, K, V, S> Sync for RawOccupiedEntryMut<'a, K, V, S> where
K: Sync,
V: Sync,
impl<'a, K, V, S> Sync for RawVacantEntryMut<'a, K, V, S> where
K: Sync,
S: Sync,
V: Sync,
impl<'a, K, V, S> Sync for RawEntryBuilder<'a, K, V, S> where
K: Sync,
S: Sync,
V: Sync,
impl<'a, K, V> Sync for OccupiedEntry<'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 OccupiedError<'a, K, V> where
K: Sync,
V: Sync,
impl Sync for RandomState
impl Sync for DefaultHasher
impl<'a, K, F> Sync for DrainFilter<'a, K, F> where
F: Sync,
K: Sync,
impl<'a, T, S> Sync for Intersection<'a, T, S> where
S: Sync,
T: Sync,
impl<'a, T, S> Sync for Difference<'a, T, S> where
S: Sync,
T: Sync,
impl<'a, T, S> Sync for SymmetricDifference<'a, T, S> where
S: Sync,
T: Sync,
impl<T> Sync for IntoIterSorted<T> where
T: Sync,
impl<'a, T> Sync for DrainSorted<'a, T> where
T: Sync,
impl<'a, K, V> Sync for OccupiedEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for OccupiedError<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for VacantEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<K, V> Sync for IntoValues<K, V> where
K: Sync,
V: Sync,
impl<'a, K, V, F> Sync for DrainFilter<'a, K, V, F> where
F: Sync,
K: Sync,
V: Sync,
impl<'a, T> Sync for Difference<'a, T> where
T: Sync,
impl<'a, T> Sync for SymmetricDifference<'a, T> where
T: Sync,
impl<'a, T> Sync for Intersection<'a, T> where
T: Sync,
impl<'a, T, F> Sync for DrainFilter<'a, T, F> where
F: Sync,
T: Sync,
impl<'a, T, F> !Sync for DrainFilter<'a, T, F>
impl Sync for TryReserveError
impl Sync for TryReserveErrorKind
impl<'a> Sync for SplitPaths<'a>
impl Sync for JoinPathsError
impl Sync for FromBytesWithNulError
impl Sync for FromVecWithNulError
impl Sync for IntoStringError
impl<'f> !Sync for VaListImpl<'f>
impl Sync for OpenOptions
impl Sync for Permissions
impl Sync for DirBuilder
impl Sync for Initializer
impl<W> Sync for IntoInnerError<W> where
W: Sync,
impl Sync for WriterPanicked
impl<W> Sync for LineWriter<W> where
W: Sync,
impl<'a> Sync for StderrLock<'a>
impl<'a> Sync for StdoutLock<'a>
impl Sync for SocketAddr
impl<'a> Sync for SocketAncillary<'a>
impl Sync for UnixStream
impl<'a> Sync for ScmCredentials<'a>
impl<'a> Sync for AncillaryData<'a>
impl Sync for UnixDatagram
impl Sync for UnixListener
impl Sync for SocketCred
impl Sync for AncillaryError
impl<T> Sync for AssertUnwindSafe<T> where
T: Sync,
impl<'a> Sync for PrefixComponent<'a>
impl<'a> Sync for Components<'a>
impl Sync for StripPrefixError
impl Sync for ChildStdin
impl Sync for ChildStdout
impl Sync for ChildStderr
impl<'a> Sync for CommandArgs<'a>
impl Sync for ExitStatus
impl Sync for ExitStatusError
impl<'a> Sync for CommandEnvs<'a>
impl<T> Sync for SyncSender<T> where
T: Send,
impl Sync for TryRecvError
impl Sync for RecvTimeoutError
impl<T> Sync for TrySendError<T> where
T: Sync,
impl Sync for BarrierWaitResult
impl Sync for WaitTimeoutResult
impl<T> Sync for PoisonError<T> where
T: Sync,
impl<T> Sync for TryLockError<T> where
T: Sync,
impl Sync for SystemTime
impl Sync for SystemTimeError
impl Sync for RawWakerVTable
impl Sync for AllocError
impl Sync for LayoutError
impl Sync for Argument
impl Sync for FormatSpec
impl Sync for Alignment
impl Sync for Count
impl Sync for FromUtf8Error
impl Sync for FromUtf16Error
impl<'a, T, F, A> Sync for DrainFilter<'a, T, F, A> where
A: Sync,
F: Sync,
T: Sync,
impl Sync for CpuidResult
impl Sync for TryFromSliceError
impl Sync for BorrowError
impl Sync for BorrowMutError
impl Sync for EscapeUnicode
impl Sync for EscapeDefault
impl Sync for EscapeDebug
impl Sync for ToLowercase
impl Sync for ToUppercase
impl Sync for CharTryFromError
impl Sync for ParseCharError
impl<I> Sync for DecodeUtf16<I> where
I: Sync,
impl Sync for DecodeUtf16Error
impl<H> Sync for BuildHasherDefault<H> where
H: Sync,
impl<Idx> Sync for RangeInclusive<Idx> where
Idx: Sync,
impl<Idx> Sync for RangeToInclusive<Idx> where
Idx: Sync,
impl<Y, R> Sync for GeneratorState<Y, R> where
R: Sync,
Y: Sync,
impl<B, C> Sync for ControlFlow<B, C> where
B: Sync,
C: Sync,
NonNull
pointers are not Sync
because the data they reference may be aliased.