z3 VS ikos

See https://cacm.acm.org/magazines/2023/6/273222-the-silent-revo... and also modern production rules engines like https://drools.org/

Oddly, back when “expert system shells” were cool people thought 10,000 rules were difficult to handle, now 1,000,000 might not be a problem at all. Back then the RETE algorithm was still under development and people were using linear search and not hash tables to do their lookups.

Also https://github.com/Z3Prover/z3

Note “the semantic web” is both an advance and a retreat in that OWL is a subset of first order logic which is really decidable and sorta kinda fast. It can do a lot but people aren’t really happy with what it can do.

Code correctness is a lost art. I requirement to think in abstractions is what scares a lot of devs to avoid it. The higher abstraction language (formal specs) focus on a dedicated language to describe code, whereas lower abstractions (code contracts) basically replace validation logic with a better model.

C# once had Code Contracts[1]; a simple yet powerful way to make formal specifications. The contracts was checked at compile time using the Z3 SMT solver[2]. It was unfortunately deprecated after a few years[3] and once removed from the .NET Runtime it was declared dead.

The closest thing C# now have is probably Dafny[4] while the C# dev guys still try to figure out how to implement it directly in the language[5].

[1] https://www.microsoft.com/en-us/research/project/code-contra...

[2] https://github.com/Z3Prover/z3

[3] https://github.com/microsoft/CodeContracts

[4] https://github.com/dafny-lang/dafny

[5] https://github.com/dotnet/csharplang/issues/105

I believe, Nim also has this functionality, although, it uses the [0]Z3Prover tool with a nim frontend [1]"DrNim" for proving.

[0]https://github.com/Z3Prover/z3

Don't get me wrong, there are times when Microsoft got it right the first time that was technically far superior to their competitors. Windows IOCP was theoretically capable of doing C10K as far back in 1994-95 when there wasn't any hardware support yet and UNIX world was bickering over how to do asynchronous I/O. Years later POSIX came up with select which was a shoddy little shit in comparison. Linux caved in finally only as recently as 2019 and implemented io_uring. Microsoft research has contributed some very interesting things to computer science like Z3 SAT solver and in collaboration with INRIA made languages like F* and Low* for formal specification and verification. But all this dwarfs in comparison to all the harm they did.

Z3 theorem prover SMT solver might help you.

Other than that, you should look at Z3 which is pretty damn good at these sort of theorems/constraints.

In the end I used Z3 Julia bindings instead. The hardest part was to get the result back from it, because I kept running into assertion violations from inside Z3

I'm trying to learn a little bit about Predicate Transformer Semantics (PTS) as part of a quick exploration of Z3.

> And you propose me instead to go and reverse engineer library Js code which I am not that proficient in, and rewrite all code in Java instead?..

Yes, rather than demand others cater to your whims, frankly.

Do you realise how hypocritical it sounds to complain that you are not proficient in Javascript, when others might not be proficient in ?

Go use Z3 if you need a prover in C++ (or Java), its far more robust (provided its the type you're after) than someones 700 LoC JavaScript implementation.

https://github.com/Z3Prover/z3

I beg to differ: there are a few tools which are comparable.

Frama-C (https://www.frama-c.com) is an open source framework that has, among its analyzers, one based on abstract interpretation (https://www.frama-c.com/fc-plugins/eva.html) that is very similar in spirit to Astree.

MOPSA (https://mopsa.lip6.fr) is another open-source project (albeit more recent, and in a more "academic" stage) that also provides abstract interpretation to analyze C programs for flaws.

NASA also released IKOS (https://github.com/NASA-SW-VnV/ikos), on the same vein.

Of course they lack the polish of a product which costs tens of thousands of euros per license, but they are open source, and their purpose is the same: to ensure code safety via formal methods, in particular abstract interpretation.

It is possible to get these tools to analyze some code and generate no complaints, which ensures absence of several kinds of problems, such as memory safety issues.

Then again, it's hard to know exactly how much they differ from Astree, since you need a license to compare them, and I don't even know if you are allowed to publish such comparisons.

I've been playing around with running IKOS (https://github.com/NASA-SW-VnV/ikos), it sounds very cool but doesn't seem to be super well maintained. I've managed to compile my project to llvm bit-code and run the IKSO on it, but the actual analysis seems to be buggy. There are open issues for the problems I encountered, but the make the analysis pretty useless (it thinks most functions are unreachable).

> https://www.absint.com/astree/index.htm

This looks interesting. It's based on abstract interpretation which is more or less the most powerful approach for imperative code available. (Because the way it works it's likely slow as hell though, I guess).

But it's closed source. One of this kind of products where you need to asks for the price… I think we all know what this means: It'll be laughably expensive.

I don't see any offer for OpenSource projects frankly.

> https://github.com/NASA-SW-VnV/ikos

Also abstract interpretation based. Looks less polished than the first one at first glance.

It's under some questionable license. According to OSI it's OpenSource. According to the FSF it's not. (The FSF argument sounds strong. They're right in my opinion. This NASA license does not look like OpenSource).

But an OpenSource project could use it for free I assume.

> https://github.com/static-analysis-engineering/CodeHawk-C

Much more constrained in scope than the other ones. But looks a little bit "too academic" imho: Uses its own C parser and such.

At least it's OpenSource under MIT license.

Thanks for the links either way! Good to know about some tools in case one would need them at some point.

> I have planned to try using them on OpenZFS for a while, but I am still busy reviewing and fixing reports made by conventional static analyzers.

Stupid question about usual C development practices (as I don't have much contact with that):

Aren't analyzers today part of the build pipeline form the get go? Especially as C is known to be full of booby traps.

Imho it shouldn't be even possible to push anything that has issues discovered by tools.

This should be the lowest barrier as most code analyzers are at most able to spot quite obvious problems (the commercial one above is likely an exception to this "rule"). When even the usual "stupid analyzer" sees issues than the code is very likely in a very bad shape.

Adding such tools later on in the development is like activating warnings post factum: You'll get drowned in issues.

Especially in such critical domains as file-systems I would actually expect that the developers are using "the best tools money can buy" (or at least the best OpenSource tools available).

"Still fixing bugs found by some code analyzer" doesn't sound like someone should have much trust with their data in something like ZFS, to be honest… The statement sounds actually quite scary to me.

They have very unusual license which I have never seen before: https://github.com/NASA-SW-VnV/ikos/blob/master/LICENSE.txt

Is anyone familiar with it? Is it OSI certified? (it's not on the OSI's site).

Yeah there are tools that require adding contracts as comments. But again, there are also friction-less tools that don't require any changes (for example a NASA one).