Trait scale_info::prelude::marker::Send

1.0.0 · source · [−]
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 Rcs 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

NonNull pointers are not Send because the data they reference may be aliased.

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.

Implementors

Auto implementors