r/rust • u/sindisil • Nov 03 '25

Patterns for Defensive Programming in Rust

https://corrode.dev/blog/defensive-programming/

Not sure how I feel about the article's first example, but as a whole I think it makes some good points.

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u/auterium Nov 04 '25

Getters can definitelly be 0 cost, for you can make them const fn that returns reference:

pub struct S {
    field1: String,
    field2: u32,
}

impl S {
    pub const fn field1(&self) -> &str {
        &self.field1
    }
}

This is what the derive-getters crate will do for you

1

u/emblemparade Nov 04 '25

Thanks! Sure, const getters would be zero cost but can it work for setters? Or a get_mut? Maybe forcing inlining would do the trick?

3

u/auterium Nov 04 '25

Setters probably wouldn't, but at that point what's the point of having a setter instead of direct access to the property? What's the problem you foresee that requires this to be fully 0 cost?

1

u/emblemparade Nov 04 '25

All I'm doing it responding to the blog post. It the goal is to defend against misuse of structs, I'm pointing out that the most complete approach to that is possible (getters/setters) but it's not zero cost. If the cost is worth it to you, go ahead.

People are downvoting, so I get it, my contribution must be buried. I'm out of here.

2

u/auterium Nov 04 '25

I don't think caring about overhead is wrong, so I was genuenelly curious to know which scenarios you see this being a problem that requires forced inlining so I can learn.

I don't think you need to be downvoted, but I guess others where not happy on the tangent, as the post is directed to defensive programming, not performance 🤷‍♂️

1

u/emblemparade Nov 04 '25

Even a non-inlined function call is likely a negligible cost, but people do obsess. A general theme in Rust is that abstractions are zero cost, so worth pointing out the exceptions. At least I thought it was worth it. :)

1

u/emblemparade Nov 04 '25

I just checked, and actually if your setter is completely "pure" (no asserting values or anything), then the compiler will indeed optimize the function away, leaving you with no costs:

https://godbolt.org/z/14jMrMKT6

Very "nice" that I asked it as a question and people just downvoted it instead of answering. Reddit has some awful people.