Rust 1.99.1 Released, Fixing Regressions in wcslen, FFI bool, and rust-lld

Rust 1.99.1 Released

The Rust team has announced the release of Rust 1.99.1, a new point release for the programming language. This update focuses on addressing specific regressions identified in previous versions, aiming to improve stability and functionality for users.

Key Regression Fixes

One significant fix in 1.99.1 addresses a missing `wcslen` symbol. Some Rust targets encountered link errors because the `wcslen` function, which can be introduced by the LLVM loop-idiom-wcslen pass for optimization, was not available in `libc` or other locations. The function is now included in Rust's compiler-builtins library as a fallback, particularly resolving issues for UEFI targets using `std`.

Another correction targets the miscompilation of FFI `bool` return values on x86_64. Previously, Rust functions returning `bool` through FFI could leave bits 1-7 of the return register unspecified, leading to incorrect values for callers. The return type is now marked for zero-extension, aligning with ABI requirements.

The release also resolves an issue where `rust-lld` failed to load `libLLVM` on macOS. This occurred when the compiler was invoked without the `rustup` proxy, as the appropriate library search path was not directly set. `rust-lld` is now built with an `rpath` entry that points to the directory containing `libLLVM.dylib`.

Updating to 1.99.1

Users with a previous Rust installation via `rustup` can update to version 1.99.1 by running the command `rustup update stable`. New users can obtain `rustup` from the official Rust website. The Rust team encourages users to test beta and nightly channels to help identify and report bugs in future releases.