fix issues pointed out in review
diff --git a/library/alloc/src/vec/into_iter.rs b/library/alloc/src/vec/into_iter.rs
index eae9ad0..8a2d254 100644
--- a/library/alloc/src/vec/into_iter.rs
+++ b/library/alloc/src/vec/into_iter.rs
@@ -164,18 +164,19 @@ fn size_hint(&self) -> (usize, Option<usize>) {
#[inline]
fn advance_by(&mut self, n: usize) -> Result<(), usize> {
let step_size = self.len().min(n);
+ let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
if mem::size_of::<T>() == 0 {
// SAFETY: due to unchecked casts of unsigned amounts to signed offsets the wraparound
// effectively results in unsigned pointers representing positions 0..usize::MAX,
// which is valid for ZSTs.
self.ptr = unsafe { arith_offset(self.ptr as *const i8, step_size as isize) as *mut T }
} else {
- let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
// SAFETY: the min() above ensures that step_size is in bounds
- unsafe {
- self.ptr = self.ptr.add(step_size);
- ptr::drop_in_place(to_drop);
- }
+ self.ptr = unsafe { self.ptr.add(step_size) };
+ }
+ // SAFETY: the min() above ensures that step_size is in bounds
+ unsafe {
+ ptr::drop_in_place(to_drop);
}
if step_size < n {
return Err(step_size);
@@ -237,11 +238,11 @@ fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
} else {
// SAFETY: same as for advance_by()
self.end = unsafe { self.end.offset(step_size.wrapping_neg() as isize) };
- let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
- // SAFETY: same as for advance_by()
- unsafe {
- ptr::drop_in_place(to_drop);
- }
+ }
+ let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
+ // SAFETY: same as for advance_by()
+ unsafe {
+ ptr::drop_in_place(to_drop);
}
if step_size < n {
return Err(step_size);
diff --git a/library/core/src/iter/adapters/flatten.rs b/library/core/src/iter/adapters/flatten.rs
index e1d665b..351fd56 100644
--- a/library/core/src/iter/adapters/flatten.rs
+++ b/library/core/src/iter/adapters/flatten.rs
@@ -412,8 +412,9 @@ fn advance_by(&mut self, n: usize) -> Result<(), usize> {
self.frontiter = None;
if let Some(ref mut back) = self.backiter {
- if let Err(advanced) = back.advance_by(rem) {
- rem -= advanced
+ match back.advance_by(rem) {
+ ret @ Ok(_) => return ret,
+ Err(advanced) => rem -= advanced,
}
}
diff --git a/library/core/src/iter/adapters/skip.rs b/library/core/src/iter/adapters/skip.rs
index e29ff12..9b89ca5 100644
--- a/library/core/src/iter/adapters/skip.rs
+++ b/library/core/src/iter/adapters/skip.rs
@@ -116,14 +116,35 @@ fn fold<Acc, Fold>(mut self, init: Acc, fold: Fold) -> Acc
}
#[inline]
+ #[rustc_inherit_overflow_checks]
fn advance_by(&mut self, n: usize) -> Result<(), usize> {
- if self.n >= n {
- self.n -= n;
- return Ok(());
+ let mut rem = n;
+
+ let step_one = self.n.saturating_add(rem);
+ match self.iter.advance_by(step_one) {
+ Ok(_) => {
+ rem -= step_one - self.n;
+ self.n = 0;
+ }
+ Err(advanced) => {
+ let advanced_without_skip = advanced.saturating_sub(self.n);
+ self.n = self.n.saturating_sub(advanced);
+ return Err(advanced_without_skip);
+ }
}
- let rem = n - self.n;
- self.n = 0;
- self.iter.advance_by(rem)
+
+ // step_one calculation may have saturated
+ if unlikely(rem > 0) {
+ return match self.iter.advance_by(rem) {
+ ret @ Ok(_) => ret,
+ Err(advanced) => {
+ rem -= advanced;
+ Err(n - rem)
+ }
+ };
+ }
+
+ Ok(())
}
}
