MaybeUninit

MaybeUninit<T> allows Rust to refer to uninitialized memory.

use std::mem::MaybeUninit;

fn main() {
    let uninit = MaybeUninit::<&i32>::uninit();
    println!("{uninit:?}");
}
This slide and its sub-slides should take about 16 minutes.

“Safe Rust is unable to refer to data that’s potentially uninitialized”

“Yet, all data arrives at the program as uninitialized.”

“Therefore, we need some bridge in the type system to allow memory to transition. MaybeUninit<T> is that type.”

“MaybeUninit<T> is very similar to the Option<T> type, although its semantics are very different. The equivalent of Option::None for MaybeUninit<T> is uninitialized memory, which is only safe to write to.”

“Reading from memory that may be uninitialized is extremely dangerous.”