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Comment by School-Cotton | Hacker News Reader

> I pretty new to Rust and I’m wondering why global mutables are hard?

They're not.

  fn main() {
      unsafe {
          COUNTER += 1;
          println!("COUNTER = {}", COUNTER);
      }
  
      unsafe {
          COUNTER += 10;
          println!("COUNTER = {}", COUNTER);
      }
  }

Global mutable variables are as easy in Rust as in any other language. Unlike other languages, Rust also provides better things that you can use instead.

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People always complain about unsafe, so I prefer to just show the safe version.

  use std::sync::Mutex;

  static LIST: Mutex<Vec<String>> = Mutex::new(Vec::new());

  fn main() -> Result<(), Box<dyn std::error::Error>> {

      LIST.lock()?.push("hello world".to_string());
      println!("{}", LIST.lock()?[0]);

      Ok(())
  }

This is completely different from the previous example.

It doesn't increment anything for starters. The example would be more convoluted if it did the same thing.

And strings in rust always delivers the WTFs I need o na Friday:

    "hello world".to_string()

    use std::sync::Mutex;
    fn main() -> Result<(), Box<dyn std::error::Error>> {
        static PEDANTRY: Mutex<u64> = Mutex::new(0);
        *PEDANTRY.lock()? += 1;
        println!("{}", PEDANTRY.lock()?);
        Ok(())
    }

Still different. Yours only increments once. Doesn't pass basic QA.

And declaring a static variable inside a function, even if in main, smells.

OP you keep comparing to doesn't even declare the variable. I'm done with you.

OP here, not showing how to declare the variable was an oversight on my part.

  static mut COUNTER: u32 = 0;

(at top-level)

If on 2024 edition, you will additionally need

  #![allow(static_mut_refs)]

Yup, your example was fine, as I said I just wanted to show a safe method too :-)

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