C*: Unifying Programming and Verification in C

(arxiv.org)

31 points | by rramadass 1 hour ago

9 comments

  • gdwatson 37 minutes ago
    Names for C successor languages are pretty well exhausted by this point, so I sympathize, but I strongly associate the name C* with a decade-old rant about C compilers’ aggressive exploitation of undefined behavior: https://www.complang.tuwien.ac.at/kps2015/proceedings/KPS_20... . (In calling it a rant I don’t mean that it’s altogether unpersuasive. Its style is just a bit spicier than I am used to seeing typeset in Computer Modern.)
  • gavinray 1 hour ago
    I really think that verification aware languages are going to become a necessity

    Wrote a bit about this recently

    https://gavinray97.github.io/blog/design-by-contract-and-eff...

    • rramadass 8 minutes ago
      The first thing people need to study is the "Correct by Construction" approach to programming as espoused by Edsger Dijkstra. Only then will the mathematical concepts used in verification aware languages start making sense and one can better understand what and how to use it.

      One of the best books to learn this from is The Correctness-by-Construction Approach to Programming by Derrick Kourie and Bruce Watson - https://link.springer.com/book/10.1007/978-3-642-27919-5

      The book actually uses Dijkstra's GCL language and wp-calculus along with Carroll Morgan's Refinement Calculus to demonstrate step-wise derivation of programs from specifications using a lot of examples.

  • jensgk 41 minutes ago
    There already is a C* : https://en.wikipedia.org/wiki/C*
    • dymk 32 minutes ago
      That C* uses .cs, but nobody is complaining about C# using that extension

      That C* was released in 1993

      Who actually cares about the name collision?

    • applfanboysbgon 32 minutes ago
      Does it matter? Is the global namespace permanently depleted because of an obscure language that nobody has used in 30 years?
  • Taikonerd 1 hour ago
    The authors cite this, but just to mention it: this sounds like F*, another proof-oriented language. (https://fstar-lang.org/)

    F* is in the ML family of languages, so it looks pretty different from C*.

  • rramadass 1 hour ago
    The "C*" language website - https://cstarlang.org/en/intro.html

    See in particular, usage benefits with LLMs (last para of https://cstarlang.org/en/intro.html) and how to use it with LLMs (https://cstarlang.org/en/tutorial/cstar-mcp.html).

    Note that the paper/language are from 2025 and so pretty recent.

  • theokrueger 53 minutes ago
    formal verification is great and all, but you can never make it as ergonomic as functional verification. this matters for agents and real people alike.

    formal verification requires a deeper understanding of underlying mechanisms to write correctly. yet nothing prevents you or your agent from changing invariants to fit the algorithm and making it incorrect.

    • ux266478 12 minutes ago
      And neither can be made as ergonomic as no verification at all. It's all about how much you need. Functional verification isn't an appropriate tool where a single bug is catastrophic.

      > yet nothing prevents you or your agent from changing invariants to fit the algorithm and making it incorrect.

      If the thing we're trying to prove is ungrounded, it's trivially true that any verification method falls apart. You're still encoding priors in your testing methodology. No matter how robust you think your testing suite is, I can still trick it if given free reign over the codebase.

    • rramadass 1 minute ago
  • glitchc 1 hour ago
    Great idea, terrible syntax.
    • ux266478 43 minutes ago
      Yeah I dislike it. Why are we babyducking sepples attributes? And what I assume to be namespace accessors? Why are logical assertions enclosed in backticks? I "get it", because it's actually kind of difficult to make a backwards compatible derivative of C that doesn't devolve into glyph soup, but this has a massive frankengrammar stink to it. The proof language is eyebrow raising to say the least.
    • ahknight 1 hour ago
      I say this about C every day.
    • rramadass 1 hour ago
      What's terrible about the syntax? Using "[[require/ensure/invariant/proof/assert/etc.]]" is actually pretty neat.

      And given that almost all C programmers are also C++ programmers, no mere syntax can faze us :-)

      • binaryturtle 1 hour ago
        In my own ranking of favourite programming languages C is at the first place. C++ comes in last. I personally hate it when people write C/C++ as if it's the very same thing. I'm quite sure there's more like me out there. :)

        Interestingly Perl comes in second, even I use it rarely (aka not at all) these days. But that's a slightly off-topic side note. :)

        • ahknight 56 minutes ago
          Perl is just C with less type safety.

          And yes, for the most part. C++ as simple shorthand for struct-attached functions and automatic memory management (no, not smart pointers; RAAI) is good. Every single thing added after that is misery and should push a modern developer to Rust, Go, or Zig (roughly in that order) where such things are implemented sanely or not at all.

          • stvltvs 37 minutes ago
            Funny I think of Perl as Bash with slightly saner syntax plus robust regexp. (said with love)
          • hnlmorg 31 minutes ago
            The only thing Perl and C have in common is the curly-brace.
        • rramadass 36 minutes ago
          For me, C++ is always in first place. It allows me to do high-level abstractions to low-level hijinks all with total control (i.e. zero-cost abstractions, Templates for compile time programming etc.) across all levels of the software stack and the full spectrum of available hardware.

          Furthermore, any C++ programmer who says they do not know C, knows neither C nor C++ (hence my preference in using C/C++ as a shorthand to encompass both and highlight the dependency of the latter on the former). I often see this in novice C++ programmers who started with "Modern C++" and identify it as something like Java/C# because of the now huge set of standard libraries and copious syntactic sugar which only compounds their confusion further.

          • applfanboysbgon 17 minutes ago
            > Furthermore, any C++ programmer who says they do not know C, knows neither C nor C++ (hence my preference in using C/C++ as a shorthand to encompass both and highlight the dependency of the latter on the former).

            Right, but this dependency is one-way. There is an entire legion of C programmers who reject C++ (most notably Linus), so claiming that almost all C programmers are also C++ programmers is a bit off.

  • bellowsgulch 32 minutes ago
    I suspect that there is a body of C programmers out here that use C on a regular basis that aren’t posting who know that using C safely is 99% just using Valgrind and some specific GCC or llvm flags and you’re done.

    They don’t reply to these threads to share that knowledge because these threads devolve into cesspools about how you should just use Rust despite the language not meeting specific requirements authors have that you have to do additional work and maintenance for in “safe” languages that you get for free in C because you don’t have to emulate it.