Can AI really rewrite Windows? Microsoft is finding out

A project being quietly researched at Microsoft is something many systems engineers consider impossible. Could AI systems systematically rewrite large amounts of C/C++ source code, much of which resides in the Windows operating system, both effectively and efficiently?

Inside Microsoft, engineering teams are experimenting with AI systems that can analyze, understand, and refactor massive codebases into Rust, a programming language known for stronger memory safety guarantees. The timeline often mentioned is 2030, though Microsoft stresses this is a research effort rather than a firm product commitment. Still, the experiment offers a rare look at how AI could reshape the future of operating system development.

Inside Microsoft’s large-scale code translation experiment

It was Galen Hunt, a top engineer at Microsoft, who first spoke up about a pretty lofty goal getting rid of C and C++ from the company's core software building blocks. Hunt's vision calls for replacing these languages with Rust on a massive scale, using a mix of code analysis, graph modeling, and AI to do the heavy lifting.

At the heart of this effort is a custom system for churning through piles of code, building out detailed maps of how different parts of the software interact. From there, AI is called in to suggest changes and make them happen without messing up the underlying structure. Their internal numbers are pretty astonishing: one engineer with AI help can refactor nearly a million lines of code in a single month. And it's worth noting Microsoft has already said they've reached the point where AI-written code is now becoming a normal part of life in their engineering teams.

Why Microsoft is pushing Rust deeper into Windows

C and C++ have long been the foundation of Windows, powering the kernel, device drivers, memory management, and core system libraries, you name it. The problem is these languages allow for super fine control of hardware, but they also make it way harder to avoid memory safety bugs like

• Those nasty buffer overflows

• Bugs where you're trying to use data that's already gone

• And data getting jumbled around in unpredictable ways

Rust approaches all this differently. By building in rules about who "owns" what data and when it's safe to use it, Rust prevents a whole class of memory errors even before the code is run. And unless you specifically tell it otherwise, Rust defaults to being super cautious about memory safety.

For Microsoft, this makes Rust a great option for the parts of Windows where speed is super important and languages that automatically clean up after themselves (garbage collection) aren't the ticket. They've already started to introduce Rust into key low-level components, expanded the available window bindings for using Rust, and even started looking at using Rust to build drivers.

Where AI-driven refactoring meets hard limits

Automated refactoring at a massive scale, a game-changer in theory, isn't quite so straightforward as the hype would have you believe. Getting the syntax right is a no-brainer, but preserving the original intent of the code? That's a different story altogether.

Despite having a decades-long history, Windows code is chock-full of assumptions about hardware, timing constraints, hidden interfaces, and even backward compatibility needs that were built up over years of development. And the thing is, a lot of these details are so ingrained, AI systems can struggle to pick up on them reliably.

There are also validation challenges. Rewritten components must maintain:

• Binary compatibility

• Predictable performance characteristics

• Stable interactions with third-party drivers

Minor slip-ups can lead to problems that will be tricky to root out with automated testing alone, and that's why Microsoft has since clarified that their initiative is more of a research experiment than a clear roadmap for future Windows releases.

What this means for engineers and Windows users

For software engineers, this whole thing should give them a heads-up on how large companies might approach the task of modernizing old codebases in the future. Instead of relying on the slow, laborious process of manual refactoring, AI-assisted systems might be able to help tackle the really big changes.

And for Windows users? Well, they'll probably not even notice anything's changed at first. If it works the way Microsoft hopes, the approach could help sniff out memory-related vulnerabilities and make Windows a bit more stable in the long run. But if Microsoft gets a bit too enthusiastic, it could end up introducing the odd subtle fault right deep down in the operating system.

For now, Microsoft is treating the whole thing as a pretty controlled experiment in software engineering. We'll just have to wait and see how well AI automation works together with human oversight, extensive testing, and a lot of careful architectural review.

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