Trait signature_core::lib::marker::Send 1.0.0[−][src]
pub unsafe auto trait Send { }
Expand description
Types that can be transferred across thread boundaries.
This trait is automatically implemented when the compiler determines it’s appropriate.
An example of a non-Send
type is the reference-counting pointer
rc::Rc
. If two threads attempt to clone Rc
s that point to the same
reference-counted value, they might try to update the reference count at the
same time, which is undefined behavior because Rc
doesn’t use atomic
operations. Its cousin sync::Arc
does use atomic operations (incurring
some overhead) and thus is Send
.
See the Nomicon for more details.
Implementations on Foreign Types
impl Send for Argument
impl Send for FormatSpec
impl Send for Alignment
impl Send for Count
impl Send for Big32x40
impl Send for Big8x3
impl Send for Number
impl Send for Decoded
impl Send for FullDecoded
impl Send for Sign
impl<'a> Send for Part<'a>
impl<'a> Send for Formatted<'a>
NonNull
pointers are not Send
because the data they reference may be aliased.
impl<T> Send for BitSpanError<T> where
T: BitStore,
impl<T> Send for MisalignError<T>
impl<'_, O, T> Send for IterMut<'_, O, T> where
T: BitStore,
O: BitOrder,
Conditionally mark BitSlice
as Send
based on its T
type argument.
In order for BitSlice
to be Send
(that is, &mut BitSlice
can be moved
across thread boundaries), it must be capable of writing to memory without
invalidating any other &BitSlice
handles that alias the same memory address.
This is true when T
is one of the fundamental integers, because no other
&BitSlice
handle is able to observe mutations, or when T
is a BitSafe
type
that implements atomic read-modify-write instructions, because other &BitSlice
types will be protected from data races by the hardware.
When T
is a non-atomic BitSafe
type, BitSlice
cannot be Send
, because
one &mut BitSlice
moved across a thread boundary may cause mutation that
another &BitSlice
may observe, but the instructions used to access memory do
not guard against data races.
A &mut 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.