问当使用不安全的Rust访问超出范围的变量时，为什么没有段错误？

EN

// function that sets a pointer to a variable with a shorter lifetime
unsafe fn what(p: &mut *const i32) {
    let a = 2;
    *p = &a;
    //let addr = *p;    // I will talk about this later
    println!("inside: {}", **p);
}

fn main() {
    let mut p: *const i32 = 0 as *const i32;
    unsafe {
        what(&mut p);

        // I thought this line would make a segfault because 'a' goes out of scope at the end of the function making the address invalid
        println!("segfault? {}", *p);

        // Even more unsettling: I can increment the address and still dereference it.
        p = ((p as usize) + 1) as *const i32;
        println!("I'm definitely missing something: {}", *p);
    }
}

inside: 2
segfault? {random number around 20000. probably uninitialized memory but why?}
I'm definitely missing something: {uninitialized memory}

let addr = *p;

segfault? 2