John Regehr

@regehr
5K Followers
978 Following
4.6K Posts
he/him
professional interestscompilers, software testing, fuzzing, formal verification, lowkey shitposting, mountains, deserts, cats
my pagehttps://john.regehr.org/
a couple weeks ago I got to hang out in the desert with my younger kid, and this coming weekend the older one and I are going backpacking. psyched!! being parents of college-aged kids, we really gotta take what we can get :)
Trump-backed Utah redistricting repeal fails to make ballot

In a blow to Republicans, an initiative that would repeal an anti-gerrymandering law will not be on Utah’s ballot this fall.

Politico
(the just-found miscompile wasn't caught by Csmith in ~8 hours of testing, either)
I do enjoy using these things in ways that don't plagiarize and don't inflict slop on people. for example, when debugging an LLVM pass, this kind of thing can actually work. like, this actually found a miscompilation bug just now, and may find more if I ask it to keep going. it's an absolutely fresh LLVM pass, there is no chance that the LLM was trained on anything it's seeing here (much less on bug fixes to it).

I'm fundamentally a tool builder, and LLM coding agents work one million times better if you give them good tools, and I wrote a thing about this

https://john.regehr.org/writing/zero_dof_programming.html

zero_dof_programming

(just a lil bit nsfw)

today I learned what a Throckmorton sign is, and now all of you need to learn this too

https://en.wikipedia.org/wiki/John_Thomas_sign

John Thomas sign - Wikipedia

sigh.... @DRMacIver...

the instructions for my headlamp indicate that if you have a sweet stache and a choking fetish, then you must pay close attention

alt: pretty much as described 😬

this looks exciting! David is incredibly good at what he does (tool support for property-based testing and test case reduction)

https://antithesis.com/blog/2026/hegel/

Hypothesis, Antithesis, synthesis

Introducing Hegel, our new family of property-based testing libraries.