Understanding Rust Error E0722: Malformed optimize Attribute
Rust Error E0722: Malformed optimize Attribute
Rust error E0722 is raised when the optimize attribute is used incorrectly, resulting in a malformed attribute. The optimize attribute can be applied to a function to control whether the optimization pipeline focuses on generating smaller code, or faster code.
Error Example and Explanation
Consider the following erroneous code example that triggers Rust Error E0722:
#![allow(unused)]
#![feature(optimize_attribute)]
fn main() {
#[optimize(something)] // error: invalid argument
pub fn something() {}
}Here, the #[optimize(something)] attribute is invalid because it needs to either be #[optimize(size)] or #[optimize(speed)], corresponding to optimizing for smaller code or faster code. The error message aptly indicates that the argument provided is invalid.
Correct Usage of the optimize Attribute
To successfully use the optimize attribute in Rust code, two different modes can be used:
1. #[optimize(size)] - Optimizes for smaller code size 2. #[optimize(speed)] - Optimizes for faster code execution
In both cases, the optimize attribute should be applied just before the function declaration. Here's an example of how to correctly use the optimize attribute:
#![allow(unused)]
#![feature(optimize_attribute)]
fn main() {
#[optimize(size)]
pub fn something() {}
}In this code example, the function 'something' has been marked with the #[optimize(size)] attribute, instructing the compiler to generate code optimized for a smaller size.
Further Reading about Rust Error E0722
You should now have a better understanding of Rust Error E0722 and the correct usage of the optimize attribute. You can find more information in RFC 2412 (see Recommended Reading).