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.
Implementors§
impl !Sync for Args
impl !Sync for ArgsOs
impl Sync for FontOptions
impl Sync for ImageSurfaceDataOwned
impl Sync for Binding
impl Sync for druid::piet::cairo::glib::Bytes
impl Sync for Checksum
impl Sync for Closure
impl Sync for Date
impl Sync for DateTime
impl Sync for EnumClass
impl Sync for EnumValue
impl Sync for druid::piet::cairo::glib::Error
impl Sync for FlagsClass
impl Sync for FlagsValue
impl Sync for druid::piet::cairo::glib::GString
impl Sync for GStringBuilder
impl Sync for MainContext
impl Sync for MainLoop
impl Sync for ParamSpec
impl Sync for ParamSpecBoolean
impl Sync for ParamSpecBoxed
impl Sync for ParamSpecChar
impl Sync for ParamSpecDouble
impl Sync for ParamSpecEnum
impl Sync for ParamSpecFlags
impl Sync for ParamSpecFloat
impl Sync for ParamSpecGType
impl Sync for ParamSpecInt64
impl Sync for ParamSpecInt
impl Sync for ParamSpecLong
impl Sync for ParamSpecObject
impl Sync for ParamSpecOverride
impl Sync for ParamSpecParam
impl Sync for ParamSpecPointer
impl Sync for ParamSpecString
impl Sync for ParamSpecUChar
impl Sync for ParamSpecUInt64
impl Sync for ParamSpecUInt
impl Sync for ParamSpecULong
impl Sync for ParamSpecUnichar
impl Sync for ParamSpecValueArray
impl Sync for ParamSpecVariant
impl Sync for Pid
impl Sync for druid::piet::cairo::glib::Source
impl Sync for ThreadPool
impl Sync for TimeZone
impl Sync for Variant
impl Sync for VariantTy
impl Sync for VariantType
impl Sync for SignalQuery
impl Sync for TypeData
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 Waker
impl Sync for alloc::string::Drain<'_>
impl Sync for AtomicWaker
impl Sync for AttrColor
impl Sync for AttrFloat
impl Sync for AttrFontDesc
impl Sync for AttrFontFeatures
impl Sync for AttrInt
impl Sync for AttrLanguage
impl Sync for AttrShape
impl Sync for AttrSize
impl Sync for AttrString
impl Sync for Attribute
impl Sync for Cancellable
impl Sync for DBusConnection
impl Sync for DBusProxy
impl Sync for File
impl Sync for FontDescription
impl Sync for GlyphString
impl Sync for InetAddress
impl Sync for InetAddressMask
impl Sync for InetSocketAddress
impl Sync for Language
impl Sync for NetworkAddress
impl Sync for PixbufFormat
impl Sync for ProxyAddress
impl Sync for SocketAddress
impl Sync for TabArray
impl Sync for UnixMountEntry
impl Sync for UnixMountPoint
impl Sync for UnixSocketAddress
impl Sync for Vfs
impl<'a> Sync for ImageSurfaceData<'a>
impl<'a> Sync for IoSlice<'a>
impl<'a> Sync for IoSliceMut<'a>
impl<'a, T> Sync for ClassRef<'a, T>where T: IsClass,
impl<'a, T> Sync for InterfaceRef<'a, T>where T: IsInterface,
impl<'a, T> Sync for OnceRef<'a, T>where T: Sync,
impl<'a, T> Sync for BorrowedObject<'a, T>where T: Send + Sync,
impl<'a, T> Sync for Drain<'a, T>where T: Sync + Array,
impl<'a, T, const CAP: usize> Sync for arrayvec::arrayvec::Drain<'a, T, CAP>where T: Sync,
impl<Dyn> Sync for DynMetadata<Dyn>where Dyn: ?Sized,
impl<Fut> Sync for FuturesUnordered<Fut>where Fut: Sync,
impl<Fut> Sync for IntoIter<Fut>where Fut: Sync + Unpin,
impl<Fut> Sync for IterPinMut<'_, Fut>where Fut: Sync,
impl<Fut> Sync for IterPinRef<'_, Fut>where Fut: Sync,
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 druid::piet::cairo::glib::bitflags::_core::cell::OnceCell<T>
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 alloc::rc::Weak<T>where T: ?Sized,
impl<T> !Sync for std::sync::mpsc::Receiver<T>
impl<T> !Sync for std::sync::mpsc::Sender<T>
impl<T> Sync for UserDataKey<T>
impl<T> Sync for OnceBox<T>where T: Sync + Send,
impl<T> Sync for Class<T>where T: IsClass,
impl<T> Sync for Interface<T>where T: IsInterface,
impl<T> Sync for druid::piet::cairo::glib::List<T>where T: Sync + GlibPtrDefault + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType> + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType>,
impl<T> Sync for PtrSlice<T>where T: Sync + GlibPtrDefault + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType> + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType>,
impl<T> Sync for druid::piet::cairo::glib::SList<T>where T: Sync + GlibPtrDefault + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType> + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType>,
impl<T> Sync for SendWeakRef<T>where T: ObjectType,
impl<T> Sync for Slice<T>where T: Sync + 'static,
impl<T> Sync for WeakRef<T>where T: ObjectType + Sync,
impl<T> Sync for ObjectImplRef<T>where T: ObjectSubclass + Send + Sync,
impl<T> Sync for ObjectImplWeakRef<T>where T: ObjectSubclass + Send + Sync,
impl<T> Sync for SyncUnsafeCell<T>where T: Sync + ?Sized,
impl<T> Sync for ChunksExactMut<'_, T>where T: Sync,
impl<T> Sync for druid::piet::cairo::glib::bitflags::_core::slice::ChunksMut<'_, T>where T: Sync,
impl<T> Sync for druid::piet::cairo::glib::bitflags::_core::slice::Iter<'_, T>where T: Sync,
impl<T> Sync for druid::piet::cairo::glib::bitflags::_core::slice::IterMut<'_, T>where T: Sync,
impl<T> Sync for RChunksExactMut<'_, T>where T: Sync,
impl<T> Sync for RChunksMut<'_, T>where T: Sync,
impl<T> Sync for AtomicPtr<T>
impl<T> Sync for Exclusive<T>where T: ?Sized,
impl<T> Sync for ThinBox<T>where T: Sync + ?Sized,
ThinBox<T> is Sync if T is Sync because the data is owned.
