Announcing Rust 1.75.0

Standard monthly release with incremental trait and pointer API improvements, but lacks major paradigm shifts or milestone status.

async fn and return-position impl Trait in traits

As announced last week, Rust 1.75 supports use of async fn and -> impl Trait in traits. However, this initial release comes with some limitations that are described in the announcement post.

It’s expected that these limitations will be lifted in future releases.

Pointer byte offset APIs

Raw pointers (*const T and *mut T) used to primarily support operations operating in units of T. For example, <*const T>::add(1) would add size_of::<T>() bytes to the pointer’s address. In some cases, working with byte offsets is more convenient, and these new APIs avoid requiring callers to cast to *const u8/*mut u8 first.

Code layout optimizations for rustc

The Rust compiler continues to get faster, with this release including the application of BOLT to our binary releases, bringing a 2% mean wall time improvements on our benchmarks. This tool optimizes the layout of the librustc_driver.so library containing most of the rustc code, allowing for better cache utilization.

We are also now building rustc with -Ccodegen-units=1, which provides more opportunity for optimizations in LLVM. This optimization brought a separate 1.5% wall time mean win to our benchmarks.

In this release these optimizations are limited to x86_64-unknown-linux-gnu compilers, but we expect to expand that over time to include more platforms.