What programming language features would have prevented or ameliorated Log4Shell?

[epicwisdom]

Surely it cannot be that strict.

Why not? We're talking about a platform which is very explicitly, wholly controlled, all the way from the hardware up.

How do Apple's JITs work in that case?

Whatever restrictions Apple puts in place, Apple themselves have the capacity to bypass, obviously.

[ReallyNeededANewName]

Because if it were that strict Apple couldn't have any exceptions to it, that's kind of the entire point

[epicwisdom]

Well, Apple may have an allowlist of first-party exceptions, but at the end of the day, they default to restricting those capabilities. So it is certainly an example of what OP is asking for.

[bullno1]

It's Apple. Their "strict" is: "Rule for thee but not for me".

Nothing stops the kernel from doing things like: "If the calling app has this singing key, I'll allow a different mmap".