# Deallocating

Next we should implement Drop so that we don't massively leak tons of resources. The easiest way is to just call `pop` until it yields None, and then deallocate our buffer. Note that calling `pop` is unneeded if `T: !Drop`. In theory we can ask Rust if `T` `needs_drop` and omit the calls to `pop`. However in practice LLVM is really good at removing simple side-effect free code like this, so I wouldn't bother unless you notice it's not being stripped (in this case it is).

We must not call `Global.deallocate` when `self.cap == 0`, as in this case we haven't actually allocated any memory.

    impl<T> Drop for Vec<T> {
        fn drop(&mut self) {
            if self.cap != 0 {
                while let Some(_) = self.pop() { }

                unsafe {
                    let c: NonNull<T> = self.ptr.into();
                    Global.deallocate(c.cast(),
                                      Layout::array::<T>(self.cap).unwrap());
                }
            }
        }
    }