[oleganza]

You don't have to play this game - you can always write within unsafe { ... } like in plain old C or C++. But people do choose to play this game because it helps them to write code that is also correct, where "correct" has an old-school meaning of "actually doing what it is supposed to do and not doing what it's not supposed to".

[ManlyBread]

That just makes it seem like there's no point in using this language in the first place.

[maccard]

Dont let perfect be the enemy of good.

Software is built on abstractions - if all your app code is written without unsafe and you have one low level unsafe block to allow for something, you get the value of rust for all your app logic and you know the actual bug is in the unsafe code

[haileys]

This is like saying there’s no point having unprivileged users if you’re going to install sudo anyway.

The point is to escalate capability only when you need it, and you think carefully about it when you do. This prevents accidental mistakes having catastrophic outcomes everywhere else.

[jstimpfle]

I think sudo is a great example. It's not much more secure than just logging in at root. It doesn't really protect malicious attackers in practice. And it's more of an annoyance than it protects against accidental mistakes in practice.

[haileys]

Unsafe isn’t a security feature per se. I think this is where a lot of the misunderstanding comes from.

It’s a speed bump that makes you pause to think, and tells reviewers to look extra closely. It also gives you a clear boundary to reason about: it must be impossible for safe callers to trigger UB in your unsafe code.

[jstimpfle]

That's my point; I think after a while you instinctly repeat a command with sudo tacked on (see XKCD), and I wonder if I'm any safer from myself like that?

I'm doubtful that those boundaries that you mention really work so great. I imagine that in practice you can easily trigger faulty behaviours in unsafe code from within safe code. Practical type systems are barely powerful enough to let you inject a proof of valid-state into the unsafe-call. Making a contract at the safe/unsafe boundary statically enforceable (I'm not doubting people do manage to do it in practice but...) probably requires a mountain of unessential complexity and/or runtime checks and less than optimal algorithms & data structures.

[MaulingMonkey]

> That's my point; I think after a while you instinctly repeat a command with sudo tacked on (see XKCD), and I wonder if I'm any safer from myself like that?

We agree that this is a dangerous / security-defeating habit to develop.

If someone realizes they're developing a pattern of such commands, it might be worth considering if there's an alternative. Some configuration or other suid binary which, being more specialized or tailor-purpouse, might be able to accomplish the same task with lower risk than a generalized sudo command.

This is often a difficult task.

Some orgs introduce additional hurdles to sudo/admin access (especially to e.g. production machines) in part to break such habits and encourage developing such alternatives.

> unsafe

There are usually safe alternatives.

If you use linters which require you to write safety documentation every time you break out an `unsafe { ... }` block, and require documentation of preconditions every time you write a new `unsafe fn`, and you have coworkers who will insist on a proper soliloquy of justification every time you touch either?

The difficult task won't be writing the safe alternative, it will be writing the unsafe one. And perhaps that difficulty will sometimes be justified, but it's not nearly so habit forming.

[haileys]

What you postulate simply doesn’t match the actual experience of programming Rust

[tialaramex]

You are of course welcome to imagine whatever you want, but why not just try it for yourself?

[pjmlp]

Because only lines marked with unsafe are suspicious, instead of every line of code.

Also the community culture matters, even though static analysis exists for C since 1979, it is still something we need to force feed many developers on C and C++ world.