Error in Rust: Variables cannot be safely passed between threads when calling async functions

Mar 7, 2022#多线程28

AI Translation

This post is translated from Chinese into English through AI.View Original

AI-generated summary

Error occurs when Rust calls async functions and variables cannot be safely passed between threads. The solution is to ensure the variable is dropped before the await keyword. Manually dropping the variable is not allowed.

This is a pseudo code snippet

async fn a() {
    let a:T = ...;//T is a type that does not implement Send
    let b = foo(a);
    boo(b).await;
}

async fn boo() -> i32 {
    ...
}

In this case, there will be an error future cannot be sent between threads safely.
The solution is to ensure that a is dropped before await

async fn a() {
    let b;
    {
        let a:T = ...;//T is a type that does not implement Send
        b = foo(a);//Here, the extracted data is Sendable
    }
    boo(b).await;
}

However, manually dropping is not allowed

async fn a() {
    let a:T = ...;//T is a type that does not implement Send
    let b = foo(a);//Here, the extracted data is Sendable
    drop(a);//Compiler does not recognize
    boo(b).await;
}

For further explanation, please refer to https://blog.csdn.net/wangjun861205/article/details/118084436