miri does not report UB for reference to uninitialized value

[gftea]

run MIRI on below rust playground, it does not report undefined behavior for the codes reference to unitialized value

// example from rust-std docs
let m = MaybeUninit::<UnsafeCell<i32>>::uninit();
unsafe { UnsafeCell::raw_get(m.as_ptr()).write(5); }
let uc = unsafe { m.assume_init() };

assert_eq!(uc.into_inner(), 5);

// reference to unitiailized value due to `&*m.as_ptr()`
let m = MaybeUninit::<UnsafeCell<i32>>::uninit();
unsafe { UnsafeCell::get(&*m.as_ptr()).write(5); }
let uc = unsafe { m.assume_init() };

assert_eq!(uc.into_inner(), 5);

[bjorn3]

cc rust-lang/unsafe-code-guidelines#386

[saethlin]

See #2518 (comment)

[RalfJung]

Also see #2518 -- this is a deliberate decision, for now. Though maybe we should keep one issue open to make it easier to find? Not sure.

[oli-obk]

I pinned #2518, turns out you can pin closed issues

[RalfJung]

Sounds good, let's close this one then.

Thanks for reporting a potential problem, @gftea.