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2024-03-21-Rust-1.77.0.md

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layout post
title Announcing Rust 1.77.0
author The Rust Release Team
release true

The Rust team is happy to announce a new version of Rust, 1.77.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.77.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.77.0.

If you'd like to help us out by testing future releases, you might consider updating locally to use the beta channel (rustup default beta) or the nightly channel (rustup default nightly). Please report any bugs you might come across!

What's in 1.77.0 stable

This release is relatively minor, but as always, even incremental improvements lead to a greater whole. A few of those changes are highlighted in this post, and others may yet fill more niche needs.

C-string literals

Rust now supports C-string literals (c"abc") which expand to a nul-byte terminated string in memory of type &CStr. This makes it easier to write code interoperating with foreign language interfaces which require nul-terminated strings, with all of the relevant error checking (e.g., lack of interior nul byte) performed at compile time.

Support for recursion in async fn

async functions previously could not call themselves due to a compiler analysis limitation. In 1.77, that limitation has been lifted, so recursive calls are permitted so long as they use some form of indirection to avoid an infinite size for the state of the function.

This means that code like this now works:

async fn fib(n : u32) -> u32 {
   match n {
       0 | 1 => 1,
       _ => Box::pin(fib(n-1)).await + Box::pin(fib(n-2)).await
   }
}

offset_of!

1.77.0 stabilizes offset_of! for struct fields, which provides access to the byte offset of the relevant public field of a struct. This macro is most useful when the offset of a field is required without an existing instance of a type. Implementing such a macro is already possible on stable, but without an instance of the type the implementation would require tricky unsafe code which makes it easy to accidentally introduce undefined behavior.

Users can now access the offset of a public field with offset_of!(StructName, field). This expands to a usize expression with the offset in bytes from the start of the struct.

Enable strip in release profiles by default

Cargo profiles which do not enable debuginfo in outputs (e.g., debug = 0) will enable strip = "debuginfo" by default.

This is primarily needed because the (precompiled) standard library ships with debuginfo, which means that statically linked results would include the debuginfo from the standard library even if the local compilations didn't explicitly request debuginfo.

Users which do want debuginfo can explicitly enable it with the debug flag in the relevant Cargo profile.

Clippy adds a new incompatible_msrv lint

The Rust project only supports the latest stable release of Rust. Some libraries aim to have an older minimum supported Rust version (MSRV), typically verifying this support by compiling in CI with an older release. However, when developing new code, it's convenient to use latest documentation and the latest toolchain with fixed bugs, performance improvements, and other improvements. This can make it easy to accidentally start using an API that's only available on newer versions of Rust.

Clippy has added a new lint, incompatible_msrv, which will inform users if functionality being referenced is only available on newer versions than their declared MSRV.

Stabilized APIs

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.77.0

Many people came together to create Rust 1.77.0. We couldn't have done it without all of you. Thanks!