News · written 8 November 2026. A summary for readers, not technical advice — check the sources at the end for the details.

Rust is a free, open-source programming language known for speed and memory safety. It is used for command-line tools, desktop apps, web services and parts of operating systems. A new stable version comes out every six weeks; the latest is Rust 1.99.

When

The Rust Release Team announced Rust 1.99.0 on 1 October 2026 and a fix release, Rust 1.99.1, on 15 October 2026. If you already have Rust installed with rustup, one command updates it:

rustup update stable

What is new in 1.99

• C-style variadic functions written in Rust. Rust could already call C functions that take a variable number of arguments (like printf). Now you can also define such functions in Rust, for the "C" and "C-unwind" ABIs, with the extra arguments read through a VaList. That makes it easier to replace C code piece by piece.
• Layout information from raw pointers: Layout::for_value_raw, mem::size_of_val_raw and mem::align_of_val_raw are now stable.
• More stable library functions, among them Vec::into_parts and Vec::from_parts, Box::into_non_null, VecDeque::retain_back, String::from_utf8_lossy_owned and std::fs::set_times.

The team notes that there are "no changes to the language semantics" in 1.99 beyond these additions.

Why 1.99.1 matters

Two weeks later, 1.99.1 fixed three problems that had slipped in:

• On x86-64, Rust functions returning a bool to other languages (through FFI) could leave part of the return value undefined — a miscompilation, meaning the compiler could produce wrong code.
• Some targets, including UEFI, got link errors about a missing wcslen function.
• On macOS, the bundled rust-lld linker could fail to start when run without the rustup proxy.

What it means for small publishers

If you build and ship software with Rust, update to 1.99.1 rather than staying on 1.99.0 — especially if your program exposes functions to C or other languages on x86-64 — and rebuild your release files so your users get the fixed code.

Sources

• The Rust Release Team — Announcing Rust 1.99.0, 1 October 2026 (features, stable APIs, update command).
• The Rust Release Team — Announcing Rust 1.99.1, 15 October 2026 (the three fixes).

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