Trait scale_info::prelude::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 Argument
impl Sync for FormatSpec
impl Sync for Alignment
impl Sync for Count
NonNull
pointers are not Sync
because the data they reference may be aliased.
Conditionally mark BitSlice
as Sync
based on its T
type argument.
In order for BitSlice
to be Sync
(that is, &BitSlice
can be copied across
thread boundaries), it must be capable of reading from memory without being
invalidated by any other &mut BitSlice
handles that alias the same memory
address.
This is true when T
is one of the fundamental integers, because no other
&mut BitSlice
handle can exist to effect mutations, or when T
is a BitSafe
type that implements atomic read-modify-write instructions, because it will
guard against other &mut BitSlice
modifications in hardware.
When T
is a non-atomic BitSafe
type, BitSlice
cannot be Sync
, because
one &BitSlice
moved across a thread boundary may read from memory that is
modified by the originally-owning thread, but the instructions used to access
memory do not guard against such data races.
A &BitSlice
over aliased memory addresses is equivalent to either a &Cell
or &AtomicT
, depending on what the radium
crate makes available for the
register width.
Implementors
impl<'_, T> Sync for scale_info::prelude::collections::vec_deque::Drain<'_, T> where
T: Sync,
Auto implementors
impl Sync for NamedFields
impl Sync for UnnamedFields
impl Sync for NameAssigned
impl Sync for NameNotAssigned
impl Sync for TypeAssigned
impl Sync for TypeNotAssigned
impl Sync for PathAssigned
impl Sync for PathNotAssigned
impl Sync for TypeDefPrimitive
impl Sync for PortableForm
impl Sync for TryReserveError
impl Sync for FpCategory
impl Sync for IntErrorKind
impl Sync for VariantBuilder
impl Sync for PortableRegistry
impl Sync for TypeDefPhantom
impl Sync for DefaultHasher
impl Sync for RandomState
impl Sync for NonZeroI16
impl Sync for NonZeroI32
impl Sync for NonZeroI64
impl Sync for NonZeroI128
impl Sync for NonZeroIsize
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 FromUtf8Error
impl Sync for FromUtf16Error
impl Sync for PhantomPinned
impl<'a, 'b> !Sync for DebugStruct<'a, 'b>
impl<'a, 'b> !Sync for DebugTuple<'a, 'b>
impl<'a, K, F> Sync for scale_info::prelude::collections::hash_set::DrainFilter<'a, K, F> where
F: Sync,
K: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::Entry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::Entry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::Iter<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::IterMut<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::Keys<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::OccupiedEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::OccupiedError<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::Range<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::VacantEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::Values<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::btree_map::ValuesMut<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::Drain<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::Iter<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::IterMut<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::Keys<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::OccupiedEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::OccupiedError<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::VacantEntry<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::Values<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V> Sync for scale_info::prelude::collections::hash_map::ValuesMut<'a, K, V> where
K: Sync,
V: Sync,
impl<'a, K, V, F> Sync for scale_info::prelude::collections::btree_map::DrainFilter<'a, K, V, F> where
F: Sync,
K: Sync,
V: Sync,
impl<'a, K, V, F> Sync for scale_info::prelude::collections::hash_map::DrainFilter<'a, K, V, F> where
F: Sync,
K: 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 RawEntryBuilder<'a, K, V, S> where
K: Sync,
S: 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 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, T> Sync for DrainSorted<'a, T> where
T: Sync,
impl<'a, T> Sync for scale_info::prelude::collections::btree_set::Difference<'a, T> where
T: Sync,
impl<'a, T> Sync for scale_info::prelude::collections::btree_set::Intersection<'a, T> where
T: Sync,
impl<'a, T> Sync for scale_info::prelude::collections::btree_set::SymmetricDifference<'a, T> where
T: Sync,
impl<'a, T, F> !Sync for scale_info::prelude::collections::linked_list::DrainFilter<'a, T, F>
impl<'a, T, F> Sync for scale_info::prelude::collections::btree_set::DrainFilter<'a, T, F> where
F: Sync,
T: Sync,
impl<'a, T, F, A> Sync for scale_info::prelude::vec::DrainFilter<'a, T, F, A> where
A: Sync,
F: Sync,
T: Sync,
impl<'a, T, S> Sync for scale_info::prelude::collections::hash_set::Difference<'a, T, S> where
S: Sync,
T: Sync,
impl<'a, T, S> Sync for scale_info::prelude::collections::hash_set::Intersection<'a, T, S> where
S: Sync,
T: Sync,
impl<'a, T, S> Sync for scale_info::prelude::collections::hash_set::SymmetricDifference<'a, T, S> where
S: Sync,
T: Sync,
impl<'a, T, S> Sync for scale_info::prelude::collections::hash_set::Union<'a, T, S> where
S: Sync,
T: Sync,
impl<H> Sync for BuildHasherDefault<H> where
H: Sync,
impl<K, V> Sync for scale_info::prelude::collections::btree_map::IntoIter<K, V> where
K: Sync,
V: Sync,
impl<K, V> Sync for scale_info::prelude::collections::btree_map::IntoKeys<K, V> where
K: Sync,
V: Sync,
impl<K, V> Sync for scale_info::prelude::collections::btree_map::IntoValues<K, V> where
K: Sync,
V: Sync,
impl<K, V> Sync for scale_info::prelude::collections::hash_map::IntoIter<K, V> where
K: Sync,
V: Sync,
impl<K, V> Sync for scale_info::prelude::collections::hash_map::IntoKeys<K, V> where
K: Sync,
V: Sync,
impl<K, V> Sync for scale_info::prelude::collections::hash_map::IntoValues<K, V> where
K: Sync,
V: Sync,
impl<N, T> Sync for FieldBuilder<N, T>
impl<S> Sync for TypeBuilder<S>
impl<T> Sync for FieldsBuilder<T>
impl<T> Sync for UntrackedSymbol<T>
impl<T> Sync for TypeDefArray<T> where
<T as Form>::Type: Sync,
impl<T> Sync for TypeDefBitSequence<T> where
<T as Form>::Type: Sync,
impl<T> Sync for TypeDefCompact<T> where
<T as Form>::Type: Sync,
impl<T> Sync for TypeDefSequence<T> where
<T as Form>::Type: Sync,
impl<T> Sync for TypeDefTuple<T> where
<T as Form>::Type: Sync,
impl<T> Sync for IntoIterSorted<T> where
T: Sync,
impl<T> Sync for BinaryHeap<T> where
T: Sync,
impl<T> Sync for Discriminant<T>
impl<T> Sync for MaybeUninit<T> where
T: Sync,
impl<T: ?Sized> Sync for ManuallyDrop<T> where
T: Sync,
impl<T: ?Sized> Sync for PhantomData<T> where
T: Sync,