Rust manual memory management

Although it’s really not recommended to do this ever, you can use malloc and free like you are used to from C. It’s not very useful, but here’s how it looks:

extern crate libc; // 0.2.65

use std::mem;

fn main() {
    unsafe {
        let my_num: *mut i32 = libc::malloc(mem::size_of::<i32>() as libc::size_t) as *mut i32;
        if my_num.is_null() {
            panic!("failed to allocate memory");
        }
        libc::free(my_num as *mut libc::c_void);
    }
}

A better approach is to use Rust’s standard library:

use std::alloc::{alloc, dealloc, Layout};

fn main() {
    unsafe {
        let layout = Layout::new::<u16>();
        let ptr = alloc(layout);

        *(ptr as *mut u16) = 42;
        assert_eq!(*(ptr as *mut u16), 42);

        dealloc(ptr, layout);
    }
}