unsafe code guidelines for hw1?

[tomtomjhj]

While implementing ART I ran into several cases where I had to use unsafe codes like raw ptr deref, std::ptr:: functions, and

unsafe { &mut *(v as &_ as *const _ as *mut _ as &mut T) ... }

Now I'm getting use-after-free errors so I decided to clean things up. But I'm still not sure how much unsafety we need in this HW.

[jeehoonkang]

ART is a pointer-based data structure, and in my opinion, you cannot avoid unsafe blocks altogether. I'd recommend you avoid unsafe blocks as much as possible, but you don't need to eradicate them.

I'd also recommend you debug your program with CLion or VSCode.

[tomtomjhj]

I believe we should use UnsafeCell<NodeBox<V>> for cursor.child instead of &mut NodeBox<V> to avoid UB.
See https://rust-lang.github.io/rust-clippy/master/index.html#cast_ref_to_mut .

[jeehoonkang]

While it is generally advisable to use UnsafeCell instead of raw pointers, replacing &mut Nodebox<V> with UnsafeCell<NodeBox<V>> is wrong: the former is essentially a pointer, while the latter is essentially a data.

[tomtomjhj]

oh that's right. I guess I mixed this up with something unrelated.