Java and Rust have actually very similar memory safety profiles. Rust let's you within the language escape the memory safety requirements whereas Java does not but both are considered memory safe languages. Rust also enforces thread safety as well which Java does not, but the slower JVM memory model doesn't let race conditions become memory safety issues whereas Rust is lower-level like Zig/C/C++ and thus thread safety could be a memory safety issue.

Zig has an identical memory safety profile to C. It has facilities to make it easier to stay memory safe, but those facilities are basically equivalent to what you have in C++ and that's equivalent memory safety profile as C.

> So among these four languages we already have four levels of memory safety, none of them is 100%

No, you've pretended like there's four when really it's Java / Rust which are safe by default and Zig/C/C++ which are unsafe by default.

One effective metric to evaluate is memory safety per LoC. Rust is ~0.2 vulnerabilities per MLoC. Java is effectively 0. C and C++ both seem to be about 1,000 vulnerabilities per MLoC. Zig is too new and hasn't had any analysis done on it, but generously it's likely at least 10-100.

So the table stakes could be defined as 1 memory safety vulnerability per MLoC.

> Java and Rust have actually very similar memory safety profiles

They really don't. Look at how many basic data structures (in the standard library or outside it) require unsafe features in Java vs Rust.

> Zig has an identical memory safety profile to C

It really doesn't. Zig gives you the same spatial memory safety as Rust and very much not like C (and violations of spatial memory safety are a bigger cause of vulnerabilities than violations of temporal memory safety).

Java may be memory safe, but no memory is safe from the JVM. :)

> Rust is ~0.2 vulnerabilities per MLoC. Java is effectively 0. C and C++ both seem to be about 1,000 vulnerabilities per MLoC. Zig is too new and hasn't had any analysis done on it, but generously it's likely at least 10-100.

You have just described six orders of magnitude in your attempt to rebut pron pointing out the four languages have four levels of memory safety.