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Prevent Zip specialization from calling __iterator_get_unchecked twice with the same index after calling next_back

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This commit is contained in:
Giacomo Stevanato 2021-03-03 21:09:01 +01:00
parent 8fd946c63a
commit 2371914a05
1 changed files with 9 additions and 4 deletions
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13
library/core/src/iter/adapters/zip.rs
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@ -13,9 +13,10 @@ use crate::iter::{InPlaceIterable, SourceIter, TrustedLen};
pub struct Zip<A, B> {
a: A,
b: B,
// index and len are only used by the specialized version of zip
// index, len and a_len are only used by the specialized version of zip
index: usize,
len: usize,
a_len: usize,
}
impl<A: Iterator, B: Iterator> Zip<A, B> {
pub(in crate::iter) fn new(a: A, b: B) -> Zip<A, B> {
@ -110,6 +111,7 @@ where
b,
index: 0, // unused
len: 0, // unused
a_len: 0, // unused
}
}
@ -184,8 +186,9 @@ where
B: TrustedRandomAccess + Iterator,
{
fn new(a: A, b: B) -> Self {
let len = cmp::min(a.size(), b.size());
Zip { a, b, index: 0, len }
let a_len = a.size();
let len = cmp::min(a_len, b.size());
Zip { a, b, index: 0, len, a_len }
}
#[inline]
@ -197,7 +200,7 @@ where
unsafe {
Some((self.a.__iterator_get_unchecked(i), self.b.__iterator_get_unchecked(i)))
}
} else if A::MAY_HAVE_SIDE_EFFECT && self.index < self.a.size() {
} else if A::MAY_HAVE_SIDE_EFFECT && self.index < self.a_len {
let i = self.index;
self.index += 1;
self.len += 1;
@ -262,6 +265,7 @@ where
for _ in 0..sz_a - self.len {
self.a.next_back();
}
self.a_len = self.len;
}
let sz_b = self.b.size();
if B::MAY_HAVE_SIDE_EFFECT && sz_b > self.len {
@ -273,6 +277,7 @@ where
}
if self.index < self.len {
self.len -= 1;
self.a_len -= 1;
let i = self.len;
// SAFETY: `i` is smaller than the previous value of `self.len`,
// which is also smaller than or equal to `self.a.len()` and `self.b.len()`