Rust solves this at compile-time with move semantics, with no runtime overhead. This feature is arguably why Rust exists, it's really useful.
Rust solves this at compile-time with move semantics, with no runtime overhead. This feature is arguably why Rust exists, it's really useful.
Rust moves are a memcpy where the source becomes effectively unitialized after the move (that is say it is undefined to access it after the move). The copies are often optimized by the compiler but it isn't guaranteed.
This actually caused some issues with rust in the kernel because moving large structs could cause you to run out the small amount of stack space availabe on kernel threads (they only allocate 8-16KB of stack compared to a typical 8MB for a userspace thread). The pinned-init crate is how they ended solving this [1].
[1] https://crates.io/crates/pinned-init
if you can always move the data that's the sweet spot for async, you just pass it down the stack and nothing matters.
all of the complexity comes in when more than one part of the code is interested in the state at the same time, which is what this thread is about.