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Clarify safety comment for A|Rc::as_ptr

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This commit is contained in:
CAD97 2020-06-30 12:35:28 -04:00
parent d8a9c61e1a
commit fc3dc723da
2 changed files with 6 additions and 10 deletions
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8
src/liballoc/rc.rs
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@ -592,11 +592,9 @@ impl<T: ?Sized> Rc<T> {
pub fn as_ptr(this: &Self) -> *const T {
let ptr: *mut RcBox<T> = NonNull::as_ptr(this.ptr);
// SAFETY: This cannot go through Deref::deref.
// Instead, we manually offset the pointer rather than manifesting a reference.
// This is so that the returned pointer retains the same provenance as our pointer.
// This is required so that e.g. `get_mut` can write through the pointer
// after the Rc is recovered through `from_raw`.
// SAFETY: This cannot go through Deref::deref or Rc::inner.
// This is required to retain raw/mut provenance such that e.g. `get_mut` can
// write through the pointer after the Rc is recovered through `from_raw`.
unsafe { &raw const (*ptr).value }
}

8
src/liballoc/sync.rs
View file

@ -591,11 +591,9 @@ impl<T: ?Sized> Arc<T> {
pub fn as_ptr(this: &Self) -> *const T {
let ptr: *mut ArcInner<T> = NonNull::as_ptr(this.ptr);
// SAFETY: This cannot go through Deref::deref.
// Instead, we manually offset the pointer rather than manifesting a reference.
// This is so that the returned pointer retains the same provenance as our pointer.
// This is required so that e.g. `get_mut` can write through the pointer
// after the Arc is recovered through `from_raw`.
// SAFETY: This cannot go through Deref::deref or RcBoxPtr::inner.
// This is required to retain raw/mut provenance such that e.g. `get_mut` can
// write through the pointer after the Rc is recovered through `from_raw`.
unsafe { &raw const (*ptr).data }
}