When Microsoft's developers and engineers sit down to code, they can now choose to work in Rust, which Redmond has added to its list of canonical languages.
“Rust now is a Tier One language at Microsoft, and that just means that it sits among C++, C# and TypeScript as the best supported languages for internal development in the company,” explained Victor Ciura, Microsoft principal engineer for the Rust tooling team, during a keynote talk today at this year’s annual RustConf, being held this week in Montréal.
Ciura said Microsoft has “paved a path” of tools and processes that support local Rust development across the entire software development lifecycle.
Rust is no stranger at Microsoft and is already present in over 100 Microsoft project repositories. The company has built Oxidizer, a set of crates to build scalable services in Rust, which have been used to build and refine the Microsoft 365 (M365) core services such as Outlook, Word, Excel, OneDrive, and SharePoint. The Copilot tech stack also owes quite a bit to Rust.
But the really messy work still lies ahead. Given the recent Windows Patch Tuesday patch deluge, no doubt one of the largest uses for Rust will be shoring up leaky C/C++ Windows code.
This is the work Rust was made for. Mozilla developer Graydon Hoare created Rust as a side project in 2006 chiefly as a high-performance language that, unlike C and C++, guarded against memory bugs.
Rewriting programs in Rust to improve performance and minimize bugs has since become a common chore for project leaders, who have Rustified everything from databases to package managers, often with the help of AI.
Redmond has already done considerable work making Rust comfy on Microsoft Visual C++ (MSVC), its native platform for compiling Windows binaries.
Notably, company engineers built rustc_codegen_utc, a custom Rust compiler code-generation backend that wires the rustc compiler directly into MSVC’s internal toolchain for Windows.
“Connecting rustc to that backend lets Rust build on the same platform investment, with perfect compatibility out of the box, rather than requiring a parallel implementation of every Windows-specific capability,” wrote Ciura in a blog post that details Redmond's rusty efforts. “The result is a unified code generation platform for Rust and C++ on Windows.”
Even with the tight Rust integration, Microsoft engineers will have their work cut out for them. One of the recurring themes of this year’s RustConf is grappling with the dangerous “unsafe” territory that comes when mixing Rust and C++ code. While the Rust compiler can flag memory errors, it typically doesn’t cover pointers into the C++ memory allocations.
Still, Redmond running towards Rust is a welcome development. In his 2025 RustConf keynote, Microsoft Azure CTO Mark Russinovich noted that ~70 percent of Windows CVEs are memory issues.
“One of the things that I realized a long time ago is that no matter how much we really want to make C and C++ better, we can't make it as good as what Rust starts with," he said. ®
Source: The register