January 3, 2026
Comment section cage match
Xr0 verifier, guarantee the safety of C programs at compile time
Promises “C but safe” — devs shout Rust, rivals, and riddles
TLDR: Xr0 aims to catch dangerous C bugs at compile time using annotations, but it’s still early and limited. Commenters split between “cool idea, show me the niche,” “just use Rust,” and brain‑teaser edge cases—making it a lively debate about how we keep old C code safe without rewriting everything.
A new tool called Xr0 claims it can check C code for nasty bugs before it runs, using simple notes in the code to stop things like freeing memory twice or following a bad pointer. The team leans into the magic—calling Xr0 a wand that checks your work—while admitting it’s still early: it only handles a slice of old‑school C (C89), and loops or recursion need manual hints for now. It’s open source and even comes with a debugger and a try-it page.
But the comments? Absolute fireworks. One camp asks why this exists when other tools already patrol this space—name‑dropping rivals like Frama‑C and CBMC—and wonders what niche Xr0 actually fills. Another digs up past headlines like “Xr0 Makes C Safer than Rust,” which instantly reopened the internet’s favorite fight: fix C or just switch to Rust. Meanwhile, a cheeky brainteaser stole the show: what if a function only allocates memory if a mythical “Turing machine halts”? Translation: what happens when the tool meets an unknowable riddle? And a pragmatic voice asks the obvious: does Xr0 need annotations everywhere, and why aren’t we enforcing basic code rules before jumping languages?
Between “quantum‑entangled safety” memes and Rust vs. C one‑liners, the vibe is equal parts curious and combative. Fans see a promising wand; skeptics want proof, polish, and a reason not to use something else instead. Either way, everyone’s clicking through to the GitHub.
Key Points
- •Xr0 is a C verifier that aims to eliminate several classes of undefined behavior using compile-time checks.
- •The tool uses C-like annotations attached to unsafe functions to convey caller obligations (e.g., allocation and freeing).
- •Xr0 currently supports a subset of C89 and lacks direct verification for loops and recursion, which are handled with axiomatic annotations.
- •The project is open source, written in pure C, with code available on GitHub and SourceHut.
- •Resources include an online try page, debugger, tutorial, theses, and a public roadmap aiming for Xr0 1.0.0 to enable C with no undefined behavior.