#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::fmt::Write;
fn main() -> Result<(), impl core::fmt::Debug> {
    let data = [1u8, 2, 3, 4, 5];
    let mut ptr: *const u8 = data.as_ptr();
    let start_rounded_down = ptr.wrapping_sub(2);
    ptr = ptr.wrapping_add(4);
    let step = 2;
    let mut out = String::new();
    while ptr != start_rounded_down {
        unsafe {
            write!(& mut out, "{}, ", * ptr)?;
        }
        ptr = ptr.wrapping_sub(step);
    }
    assert_eq!(out, "5, 3, 1, ");
    std::fmt::Result::Ok(())
}