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use wrapping_offset; fix logic error in nth

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This commit is contained in:
Ralf Jung
2018-07-18 18:29:44 +02:00
parent c7d90d1a50
commit cbdba2b4c2
1 changed files with 12 additions and 10 deletions
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src/libcore/slice/mod.rs
+12 -10
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@@ -546,7 +546,7 @@ pub fn iter(&self) -> Iter<T> {
assume(!ptr.is_null());
let end = if mem::size_of::<T>() == 0 {
(ptr as usize).wrapping_add(self.len()) as *const _
(ptr as *const u8).wrapping_offset(self.len() as isize) as *const T
} else {
ptr.offset(self.len() as isize)
};
@@ -578,7 +578,7 @@ pub fn iter_mut(&mut self) -> IterMut<T> {
assume(!ptr.is_null());
let end = if mem::size_of::<T>() == 0 {
(ptr as usize).wrapping_add(self.len()) as *mut _
(ptr as *mut u8).wrapping_offset(self.len() as isize) as *mut T
} else {
ptr.offset(self.len() as isize)
};
@@ -2354,7 +2354,7 @@ fn make_slice(&self) -> &'a [T] {
unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
if mem::size_of::<T>() == 0 {
// This is *reducing* the length. `ptr` never changes with ZST.
self.end = (self.end as isize).wrapping_sub(offset) as * $raw_mut T;
self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
self.ptr
} else {
let old = self.ptr;
@@ -2369,7 +2369,7 @@ unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
#[inline(always)]
unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T {
if mem::size_of::<T>() == 0 {
self.end = (self.end as isize).wrapping_sub(offset) as * $raw_mut T;
self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
self.ptr
} else {
self.end = self.end.offset(-offset);
@@ -2432,12 +2432,14 @@ fn count(self) -> usize {
#[inline]
fn nth(&mut self, n: usize) -> Option<$elem> {
if n >= self.len() {
// This iterator is now empty. The way we encode the length of a non-ZST
// iterator, this works for both ZST and non-ZST.
// For a ZST we would usually do `self.end = self.ptr`, but since
// we will not give out an reference any more after this there is no
// way to observe the difference except for raw pointers.
self.ptr = self.end;
// This iterator is now empty.
if mem::size_of::<T>() == 0 {
// We have to do it this way as `ptr` may never be 0, but `end`
// could be (due to wrapping).
self.end = self.ptr;
} else {
self.ptr = self.end;
}
return None;
}
// We are in bounds. `offset` does the right thing even for ZSTs.