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VecDeque: fix incorrect &mut aliasing in IterMut::next/next_back

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This commit is contained in:
Ralf Jung 2020-09-19 11:08:47 +02:00
parent efbaa41306
commit f251dc446f
1 changed files with 24 additions and 7 deletions
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31
library/alloc/src/collections/vec_deque.rs
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@ -14,6 +14,7 @@ use core::cmp::{self, Ordering};
use core::fmt;
use core::hash::{Hash, Hasher};
use core::iter::{repeat_with, FromIterator, FusedIterator};
use core::marker::PhantomData;
use core::mem::{self, replace, ManuallyDrop};
use core::ops::{Index, IndexMut, Range, RangeBounds, Try};
use core::ptr::{self, NonNull};
@ -982,7 +983,12 @@ impl<T> VecDeque<T> {
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter_mut(&mut self) -> IterMut<'_, T> {
IterMut { tail: self.tail, head: self.head, ring: unsafe { self.buffer_as_mut_slice() } }
IterMut {
tail: self.tail,
head: self.head,
ring: unsafe { self.buffer_as_mut_slice() },
phantom: PhantomData,
}
}
/// Returns a pair of slices which contain, in order, the contents of the
@ -1175,6 +1181,7 @@ impl<T> VecDeque<T> {
head,
// The shared reference we have in &mut self is maintained in the '_ of IterMut.
ring: unsafe { self.buffer_as_mut_slice() },
phantom: PhantomData,
}
}
@ -2662,15 +2669,19 @@ impl<T> FusedIterator for Iter<'_, T> {}
/// [`iter_mut`]: VecDeque::iter_mut
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IterMut<'a, T: 'a> {
ring: &'a mut [T],
ring: *mut [T],
tail: usize,
head: usize,
phantom: PhantomData<&'a mut [T]>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let (front, back) = RingSlices::ring_slices(&*self.ring, self.head, self.tail);
// FIXME: this creates a reference to the full ring, including the part
// to which we already handed out mutable references via `next()`. This
// is an aliasing violation.
let (front, back) = RingSlices::ring_slices(unsafe { &*self.ring }, self.head, self.tail);
f.debug_tuple("IterMut").field(&front).field(&back).finish()
}
}
@ -2689,7 +2700,7 @@ impl<'a, T> Iterator for IterMut<'a, T> {
unsafe {
let elem = self.ring.get_unchecked_mut(tail);
Some(&mut *(elem as *mut _))
Some(&mut *elem)
}
}
@ -2703,7 +2714,10 @@ impl<'a, T> Iterator for IterMut<'a, T> {
where
F: FnMut(Acc, Self::Item) -> Acc,
{
let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
// FIXME: this creates a reference to the full ring, including the part
// to which we already handed out mutable references via `next()`. This
// is an aliasing violation.
let (front, back) = RingSlices::ring_slices(unsafe { &mut *self.ring }, self.head, self.tail);
accum = front.iter_mut().fold(accum, &mut f);
back.iter_mut().fold(accum, &mut f)
}
@ -2735,7 +2749,7 @@ impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
unsafe {
let elem = self.ring.get_unchecked_mut(self.head);
Some(&mut *(elem as *mut _))
Some(&mut *elem)
}
}
@ -2743,7 +2757,10 @@ impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
where
F: FnMut(Acc, Self::Item) -> Acc,
{
let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
// FIXME: this creates a reference to the full ring, including the part
// to which we already handed out mutable references via `next()`. This
// is an aliasing violation.
let (front, back) = RingSlices::ring_slices(unsafe { &mut *self.ring }, self.head, self.tail);
accum = back.iter_mut().rfold(accum, &mut f);
front.iter_mut().rfold(accum, &mut f)
}