rust-coding-standards

Rust Coding Standards

Purpose: Master Rust's ownership system, type safety, and zero-cost abstractions for building safe, concurrent, and performant systems.

Level 1: Quick Reference

Core Principles

• Ownership: Each value has exactly one owner
• Borrowing: References allow multiple readers XOR one writer
• Zero-cost abstractions: High-level code compiles to optimal machine code
• Explicit over implicit: No hidden allocations or control flow

Ownership & Borrowing Cheat Sheet

// Ownership transfer (move)
let s1 = String::from("hello");
let s2 = s1; // s1 is now invalid

// Immutable borrow (multiple allowed)
let s = String::from("hello");
let r1 = &s;
let r2 = &s;
println!("{} and {}", r1, r2); // OK

// Mutable borrow (exclusive)
let mut s = String::from("hello");
let r1 = &mut s;
r1.push_str(" world");

// Copy types (stack-only)
let x = 5;
let y = x; // x is still valid (i32 implements Copy)

Result & Option

// Option: value may be absent
let name = find_user(42).map(|u| u.name).unwrap_or("Anonymous".into());

// Early return with ?
fn process() -> Result<(), Error> {
    let config = parse_config("app.toml")?;
    Ok(())
}

Essential Checklist

• cargo clippy -- -D warnings
• cargo fmt -- --check
• cargo test
• cargo doc --no-deps
• cargo audit
• Document all unsafe blocks

Memory Safety Rules

1. No data races: Compiler enforces at compile time
2. No null pointers: Use Option<T> instead
3. No dangling pointers: Borrow checker prevents
4. No use-after-free: Ownership system prevents
5. No buffer overflows: Bounds checking

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Level 2: Implementation Guide

Ownership System

The Three Rules

1. Each value has a variable that's its owner
2. There can only be one owner at a time
3. When the owner goes out of scope, the value is dropped

fn takes_ownership(s: String) {
    println!("{}", s);
} // s dropped here

fn main() {
    let s = String::from("hello");
    takes_ownership(s); // s moved
    // println!("{}", s); // Error: value borrowed after move
}

// Return ownership
fn gives_ownership() -> String {
    String::from("hello")
}