How well can LLMs reason about avoiding UB? This seems like one of those things where no matter how much code you look at, you can still easily get wrong (as humans frequently do).
Fair point on UB — LLMs absolutely do not reason about it (or anything else). They just reproduce the lowest-common-denominator patterns that happened to survive in the wild.
I’m not claiming the generated C is “safe” or even close. I am sure that in practice it still has plenty of time-bombs, but empirically, for the narrow WASM tasks I tried, the raw C suggestions were dramatically less wrong than the equivalent JavaScript ones — fewer obvious foot-guns, better idioms, etc.
So my original “noticeably better” was really about “fewer glaring mistakes per 100 lines” rather than “actually correct.” I still end up rewriting or heavily massaging almost everything, but it’s a better starting point than the JS ever was.
