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Обсуждение на тему: Rust send

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Rust send

This trait is automatically implemented when the compiler determines its appropriate. An example of a non-send type is the reference-counting pointer rcrc. 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 doesnt use atomic operations. Its cousin syncarc does use atomic operations (incurring some overhead) and thus is send. Маркерный типаж send указывает, что владение типом реализующим send, может передаваться между потоками. По этой причине rct реализован для использования в однопоточных ситуациях, когда вы не хотите платить за снижение производительности. Следовательно, система типов rust и ограничений типажа гарантируют, что вы никогда не сможете случайно небезопасно отправлять значение rct между потоками.

В rust всё множество типов делится на два вида те, которые реализуют трейт send, что означает, что эти типы можно безопасно перемещать между потоками, и те, которые его не реализуют (!send), что, соответственно, значит противоположное. Если все компоненты типа являются send, то и он сам является send, что покрывает большинство типов. The send and sync traits are fundamental traits provided by the rust standard library for concurrent programming. Heres a brief overview of these traits send trait the send trait is implemented by types that can be transferred safely between threads. It indicates that a type can be moved or sent to a different thread, allowing the safe sharing of data across thread boundaries. Sync trait the sync trait is implemented by types that can be shared safely between threads without causing any data races. Hence the ownership model is an important part of rusts send thread safety, and may be the reason that send is less intuitive than sync when comparing with other languages.

Using the above definitions, it should be apparent why there are few examples of types that are sync but not send. If an object can be used safely by two threads at the same time (sync) then it can be used safely by two threads at different times (send). In this comprehensive tutorial, well explore rusts secret weapons for bulletproof thread safety the send and sync traits. Heres what well cover step-by-step core concurrency and thread safety concepts in rust. So lets get started on our journey towards mastering concurrent rust! Why concurrency safety matters. Because rct is not marked send, rusts type system and trait bounds ensure that we can never forget and accidentally send an rct value across threads unsafely. We tried to do this in listing 16-14, and we got an error that said the trait send is not implemented for rcmutexi32.

Any type that is composed entirely of send types is automatically marked as send as well. For people writing safe code, you dont really need to understand these traits on a deep level, only enough to satisfy the compiler when it spits errors at you (or switch from std threads to crossbeam scoped threads to make errors go away). However if youre writing unsafe concurrent code, such as having a &unsafecellt hand out &t and &mut t, you need to understand send and sync at a more. In rust, closures are self-contained blocks of code that can capture variables from their enclosing scopes. This capture allows closures to access and manipulate the captured variables. .