I guess one could claim that some feature is useful because it eliminates certain classes of bugs while another is useless because it eliminates certain classes of bugs (which happens to be the more impactful subset of the former class), it's just not a very compelling claim, especially the way you presented it, which is:
Something bad happens, say an attacker steals my data. Rust is useful because I can eliminate spatial and temporal safety as the cause, leaving only all others, while in Zig I can eliminate spatial unsafety as the cause (leaving all others), but that's just as useless as C, where I can eliminate neither spatial nor temporal unsafety as the cause.
I can see how it may be reasonable to argue that all are equally useless, but given that spatial unsafety is the largest subclass of unsafety that causes security vulnerabilities, I'm not convinced by the argument that eliminating it is completely useless while eliminating a somewhat larger class (i.e. adding a smaller marginal benefit than the first step) becomes very useful.
Have you noticed how zero is categorically different from the other numbers, even the very small ones? It's an additive identity. No matter how often we sum together zeroes, the answer is still zero and that won't work for other values. Being the additive identity is categorically different, even though it might seem as though zero is just even smaller than a tenth or a millionth, it's different.
In (safe) Rust we categorically don't have type unsafety. Safe Rust function A doesn't have unsafety, and function B which calls it doesn't have unsafety, and function C which calls that doesn't either and so on forever. So in the exercise we talked about the answer is that the fault won't be anywhere in the safe Rust. But because we don't have this in "safe" Zig even though you say there's spatial safety, oops the lack of temporal safety means our apparently OK code might induce the spatial safety issues we thought couldn't exist.
It's OK, the C++ Convener is absolutely convinced of the same line of thinking as you. Surely if they can just keep finding adjustments to make C++ fractionally safer it'll be as safe as Rust. Right? If every three years they make it 10% less unsafe, surely in thirty years it's... oh right, about 65% less unsafe. Huh.
> In (safe) Rust we categorically don't have type unsafety
This is very inaccurate. Simple (i.e. non-dependent) types can describe very, very few properties. 99% of correctness properties cannot be described with simple types at all. That is exactly why, from ATS's vantage point, Rust is about as "safe" as Assembly; its types can guarantee almost nothing, while ATS can guarantee virtually everything.
So now the question is, with what little simple types give us (which is still useful), how much are we willing to pay for what confidence in their soundness. After all, Rust doesn't actually give us 100% safety, because we interact with C code etc.. But it does give us some higher confidence than the one given to us by Zig. So now the question is, since we don't have 100% confidence anyway - there are no zeros or ones here, neither on cost nor on the benefit side - how much are we willing to pay for what amount of added confidence?
Some people find the cost of Rust to be worth the added confidence; some don't. There is no binary line here.
> It's OK, the C++ Convener is absolutely convinced of the same line of thinking as you. Surely if they can just keep finding adjustments to make C++ fractionally safer it'll be as safe as Rust.
I'm not interested in making C++ as safe as Rust. For applications programming I use Java, which is somewhat safer than Rust, and for low-level code, I'm much more interested in other correctness properties than just safety. Safety gives me some small portion of the correctness I want, and it's great when that small portion is mostly free, but the bang-for-the-buck that I get from Rust is too low for me. I pay for all this complication in exchange for only guaranteeing no UAF? For that effort, I want a lot more.
> After all, Rust doesn't actually give us 100% safety, because we interact with C code etc..
And so, after all this long thread you're back to just saying you weren't actually talking about safe Rust in the conversation about safe Rust. It was all a big waste of my time.
No, I was talking about safe Rust, which also interacts with potentially unsafe C code, you know. What do you think schedules the threads running your safe code? How do you think your safe code reads from a socket?
I guess one could claim that some feature is useful because it eliminates certain classes of bugs while another is useless because it eliminates certain classes of bugs (which happens to be the more impactful subset of the former class), it's just not a very compelling claim, especially the way you presented it, which is:
Something bad happens, say an attacker steals my data. Rust is useful because I can eliminate spatial and temporal safety as the cause, leaving only all others, while in Zig I can eliminate spatial unsafety as the cause (leaving all others), but that's just as useless as C, where I can eliminate neither spatial nor temporal unsafety as the cause.
I can see how it may be reasonable to argue that all are equally useless, but given that spatial unsafety is the largest subclass of unsafety that causes security vulnerabilities, I'm not convinced by the argument that eliminating it is completely useless while eliminating a somewhat larger class (i.e. adding a smaller marginal benefit than the first step) becomes very useful.