rustRust unsafe borrow example

An example of an unsafe borrow in Rust is when a reference to a value is used after that value has been dropped. This can lead to a segmentation fault or other undefined behavior.

let mut x = 5;
let y = &mut x;
drop(x);
println!("{}", y);

Output example

thread 'main' panicked at 'already borrowed: BorrowMutError', src/libcore/result.rs:1165:5

Code explanation

• let mut x = 5;: Declares a mutable variable x with the value 5.
• let y = &mut x;: Creates a mutable reference y to x.
• drop(x);: Drops the value of x.
• println!("{}", y);: Attempts to print the value of y, which is a reference to x that has already been dropped.

Helpful links

• Rust Reference
• Rust Borrowing Rules

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