pub unsafe auto trait Sync { }Expand description
core
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.
A shorter overview of how Sync and Send relate to referencing:
&TisSendif and only ifTisSync&mut TisSendif and only ifTisSend&Tand&mut TareSyncif and only ifTisSync
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.
Implementors§
impl !Sync for LocalWaker
impl !Sync for Arguments<'_>
impl !Sync for Args
impl !Sync for ArgsOs
impl Sync for RawId
impl Sync for devela::_dep::sdl2::event::Event
This does not auto-derive because User’s data fields can be used to
store pointers to types that are !Sync. Dereferencing these as pointers
requires using unsafe and ensuring your own safety guarantees.
impl Sync for devela::_dep::sdl3::event::Event
This does not auto-derive because User’s data fields can be used to
store pointers to types that are !Sync. Dereferencing these as pointers
requires using unsafe and ensuring your own safety guarantees.
impl Sync for ExampleEnumIntU8
Available on
doc or test only.impl Sync for devela::_core::ffi::c_str::Bytes<'_>
impl Sync for devela::_core::sync::atomic::AtomicBool
impl Sync for devela::_core::sync::atomic::AtomicI8
impl Sync for devela::_core::sync::atomic::AtomicI16
impl Sync for devela::_core::sync::atomic::AtomicI32
impl Sync for devela::_core::sync::atomic::AtomicI64
impl Sync for devela::_core::sync::atomic::AtomicIsize
impl Sync for devela::_core::sync::atomic::AtomicU8
impl Sync for devela::_core::sync::atomic::AtomicU16
impl Sync for devela::_core::sync::atomic::AtomicU32
impl Sync for devela::_core::sync::atomic::AtomicU64
impl Sync for devela::_core::sync::atomic::AtomicUsize
impl Sync for devela::_dep::_alloc::string::Drain<'_>
impl Sync for BoxBytes
impl Sync for Graph
impl Sync for devela::_dep::ffmpeg_the_third::Frame
impl Sync for devela::_dep::ffmpeg_the_third::Packet
impl Sync for devela::_dep::ffmpeg_the_third::util::format::pixel::Descriptor
impl Sync for PyDateTime_CAPI
impl Sync for PyBackedBytes
impl Sync for PyBackedStr
impl Sync for devela::_dep::rodio::cpal::platform::AlsaDevices
impl Sync for devela::_dep::sdl2::EventSubsystem
impl Sync for devela::_dep::sdl2::SensorSubsystem
impl Sync for TimerSubsystem
impl Sync for devela::_dep::sdl3::EventSubsystem
impl Sync for AbortHandle
impl Sync for devela::all::AtomicBool
impl Sync for Waker
impl Sync for bytes::bytes::Bytes
impl Sync for BytesMut
impl Sync for Collector
impl Sync for Unparker
impl Sync for crossbeam_utils::thread::Scope<'_>
impl Sync for GuardNoSend
impl<'a> Sync for Notified<'a>
impl<'a> Sync for IoSlice<'a>
impl<'a> Sync for IoSliceMut<'a>
impl<'a, 'bump> Sync for devela::_dep::bumpalo::collections::string::Drain<'a, 'bump>
impl<'a, 'bump, T> Sync for devela::_dep::bumpalo::collections::vec::Drain<'a, 'bump, T>where
T: Sync,
impl<'a, R, G, T> Sync for MappedReentrantMutexGuard<'a, R, G, T>
impl<'a, R, G, T> Sync for ReentrantMutexGuard<'a, R, G, T>
impl<'a, R, T> Sync for lock_api::mutex::MappedMutexGuard<'a, R, T>
impl<'a, R, T> Sync for lock_api::mutex::MutexGuard<'a, R, T>
impl<'a, R, T> Sync for lock_api::rwlock::MappedRwLockReadGuard<'a, R, T>
impl<'a, R, T> Sync for lock_api::rwlock::MappedRwLockWriteGuard<'a, R, T>
impl<'a, R, T> Sync for RwLockUpgradableReadGuard<'a, R, T>
impl<'a, T> Sync for devela::_dep::tokio::sync::MappedMutexGuard<'a, T>
impl<'a, T> Sync for devela::_dep::ureq::http::header::Drain<'a, T>where
T: Sync,
impl<'a, T> Sync for devela::_dep::ureq::http::header::Iter<'a, T>where
T: Sync,
impl<'a, T> Sync for devela::_dep::ureq::http::header::IterMut<'a, T>where
T: Sync,
impl<'a, T> Sync for ValueDrain<'a, T>where
T: Sync,
impl<'a, T> Sync for ValueIterMut<'a, T>where
T: Sync,
impl<'a, T> Sync for OnceRef<'a, T>where
T: Sync,
impl<'a, T> Sync for smallvec::Drain<'a, T>
impl<'a, T, const CAP: usize> Sync for arrayvec::arrayvec::Drain<'a, T, CAP>where
T: Sync,
impl<'bump, T> Sync for devela::_dep::bumpalo::collections::vec::IntoIter<'bump, T>where
T: Sync,
impl<Dyn> Sync for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<K, V, S, A> Sync for devela::_dep::hashbrown::hash_map::OccupiedEntry<'_, K, V, S, A>
impl<K, V, S, A> Sync for RawOccupiedEntryMut<'_, K, V, S, A>
impl<R, G> Sync for RawReentrantMutex<R, G>
impl<R, G, T> Sync for ReentrantMutex<R, G, T>
impl<R, T> Sync for lock_api::mutex::Mutex<R, T>
impl<R, T> Sync for lock_api::rwlock::RwLock<R, T>
impl<R, T> Sync for lock_api::rwlock::RwLockReadGuard<'_, R, T>
impl<R, T> Sync for lock_api::rwlock::RwLockWriteGuard<'_, R, T>
impl<T> !Sync for *const Twhere
T: ?Sized,
impl<T> !Sync for *mut Twhere
T: ?Sized,
impl<T> !Sync for Cell<T>where
T: ?Sized,
impl<T> !Sync for devela::all::MpscReceiver<T>
impl<T> !Sync for devela::all::OnceCell<T>
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 RefCell<T>where
T: ?Sized,
impl<T> !Sync for UnsafeCell<T>where
T: ?Sized,
impl<T> Sync for SyncUnsafeCell<T>
impl<T> Sync for devela::_core::slice::ChunksExactMut<'_, T>where
T: Sync,
impl<T> Sync for devela::_core::slice::ChunksMut<'_, T>where
T: Sync,
impl<T> Sync for devela::_core::slice::Iter<'_, T>where
T: Sync,
impl<T> Sync for devela::_core::slice::IterMut<'_, T>where
T: Sync,
impl<T> Sync for devela::_core::slice::RChunksExactMut<'_, T>where
T: Sync,
impl<T> Sync for devela::_core::slice::RChunksMut<'_, T>where
T: Sync,
impl<T> Sync for devela::_core::sync::atomic::AtomicPtr<T>
impl<T> Sync for Exclusive<T>where
T: ?Sized,
impl<T> Sync for ThinBox<T>
ThinBox<T> is Sync if T is Sync because the data is owned.
impl<T> Sync for devela::_dep::_alloc::collections::linked_list::Iter<'_, T>where
T: Sync,
impl<T> Sync for devela::_dep::_alloc::collections::linked_list::IterMut<'_, T>where
T: Sync,
impl<T> Sync for devela::_dep::_std::sync::mpmc::Receiver<T>where
T: Send,
impl<T> Sync for devela::_dep::_std::sync::mpmc::Sender<T>where
T: Send,
impl<T> Sync for devela::_dep::_std::sync::MappedMutexGuard<'_, T>
impl<T> Sync for devela::_dep::_std::sync::MappedRwLockReadGuard<'_, T>
impl<T> Sync for devela::_dep::_std::sync::MappedRwLockWriteGuard<'_, T>
impl<T> Sync for ReentrantLock<T>
impl<T> Sync for ReentrantLockGuard<'_, T>
impl<T> Sync for Codec<T>
impl<T> Sync for PyBuffer<T>
impl<T> Sync for Py<T>
impl<T> Sync for GILOnceCell<T>
impl<T> Sync for GILProtected<T>where
T: Send,
impl<T> Sync for ReadHalf<T>where
T: Sync,
impl<T> Sync for WriteHalf<T>where
T: Sync,
impl<T> Sync for devela::_dep::tokio::sync::Mutex<T>
impl<T> Sync for devela::_dep::tokio::sync::MutexGuard<'_, T>
impl<T> Sync for devela::_dep::tokio::sync::OnceCell<T>
impl<T> Sync for OwnedMutexGuard<T>
impl<T> Sync for OwnedRwLockWriteGuard<T>
impl<T> Sync for devela::_dep::tokio::sync::RwLock<T>
impl<T> Sync for RwLockMappedWriteGuard<'_, T>
impl<T> Sync for devela::_dep::tokio::sync::RwLockReadGuard<'_, T>
impl<T> Sync for devela::_dep::tokio::sync::RwLockWriteGuard<'_, T>
impl<T> Sync for devela::_dep::tokio::task::JoinHandle<T>where
T: Send,
impl<T> Sync for devela::all::Arc<T>
impl<T> Sync for devela::all::ArcWeak<T>
impl<T> Sync for devela::all::Atomic<T>
impl<T> Sync for devela::all::MpscSender<T>where
T: Send,
impl<T> Sync for devela::all::Mutex<T>
T must be Send for Mutex to be Sync.
This ensures that the protected data can be accessed safely from multiple threads
without causing data races or other unsafe behavior.
Mutex<T> provides mutable access to T to one thread at a time. However, it’s essential
for T to be Send because it’s not safe for non-Send structures to be accessed in
this manner. For instance, consider Rc, a non-atomic reference counted smart pointer,
which is not Send. With Rc, we can have multiple copies pointing to the same heap
allocation with a non-atomic reference count. If we were to use Mutex<Rc<_>>, it would
only protect one instance of Rc from shared access, leaving other copies vulnerable
to potential data races.
Also note that it is not necessary for T to be Sync as &T is only made available
to one thread at a time if T is not Sync.
impl<T> Sync for devela::all::MutexGuard<'_, T>
T must be Sync for a MutexGuard<T> to be Sync
because it is possible to get a &T from &MutexGuard (via Deref).
impl<T> Sync for NonZero<T>where
T: ZeroablePrimitive + Sync,
impl<T> Sync for OnceLock<T>
impl<T> Sync for devela::all::RwLock<T>
impl<T> Sync for devela::all::RwLockReadGuard<'_, T>
impl<T> Sync for devela::all::RwLockWriteGuard<'_, T>
impl<T> Sync for SpinLock<T>where
T: Send,
Available on crate feature
unsafe_sync only.impl<T> Sync for devela::all::ThreadJoinHandle<T>
impl<T> Sync for Injector<T>where
T: Send,
impl<T> Sync for Stealer<T>where
T: Send,
impl<T> Sync for crossbeam_epoch::atomic::Atomic<T>
impl<T> Sync for AtomicCell<T>where
T: Send,
impl<T> Sync for CachePadded<T>where
T: Sync,
impl<T> Sync for ShardedLock<T>
impl<T> Sync for ShardedLockReadGuard<'_, T>
impl<T> Sync for ShardedLockWriteGuard<'_, T>
impl<T> Sync for crossbeam_utils::thread::ScopedJoinHandle<'_, T>
impl<T> Sync for OnceBox<T>
impl<T> Sync for signal_hook::low_level::channel::Channel<T>where
T: Send,
impl<T, A> !Sync for UniqueRc<T, A>
impl<T, A> !Sync for Rc<T, A>
impl<T, A> !Sync for devela::all::RcWeak<T, A>
impl<T, A> Sync for devela::_dep::_alloc::collections::linked_list::Cursor<'_, T, A>
impl<T, A> Sync for devela::_dep::_alloc::collections::linked_list::CursorMut<'_, T, A>
impl<T, A> Sync for devela::_dep::_alloc::collections::vec_deque::Drain<'_, T, A>
impl<T, A> Sync for devela::_dep::_alloc::sync::Arc<T, A>
impl<T, A> Sync for UniqueArc<T, A>
impl<T, A> Sync for devela::_dep::_alloc::sync::Weak<T, A>
impl<T, A> Sync for devela::_dep::_alloc::vec::Drain<'_, T, A>
impl<T, A> Sync for devela::_dep::_alloc::vec::IntoIter<T, A>
impl<T, A> Sync for devela::_dep::allocator_api2::boxed::Box<T, A>
impl<T, A> Sync for devela::_dep::allocator_api2::vec::Drain<'_, T, A>
impl<T, A> Sync for devela::_dep::allocator_api2::vec::IntoIter<T, A>
impl<T, A> Sync for devela::_dep::hashbrown::hash_table::OccupiedEntry<'_, T, A>
impl<T, A> Sync for LinkedList<T, A>
impl<T, F> Sync for LazyLock<T, F>
impl<T, F> Sync for Lazy<T, F>
impl<T, F, S> Sync for scopeguard::ScopeGuard<T, F, S>
impl<T, U> Sync for OwnedMappedMutexGuard<T, U>
impl<T, U> Sync for OwnedRwLockMappedWriteGuard<T, U>
impl<T, U> Sync for OwnedRwLockReadGuard<T, U>
impl<T: Sync> Sync for BareBox<T>
Available on crate feature
unsafe_sync only.impl<T: Sync> Sync for CacheAlign<T>
Available on crate feature
unsafe_sync only.