From fc3dc723da8daef495a170e02efb38093e05215e Mon Sep 17 00:00:00 2001 From: CAD97 Date: Tue, 30 Jun 2020 12:35:28 -0400 Subject: Clarify safety comment for A|Rc::as_ptr --- src/liballoc/rc.rs | 8 +++----- src/liballoc/sync.rs | 8 +++----- 2 files changed, 6 insertions(+), 10 deletions(-) (limited to 'src/liballoc') diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs index 423122a6900..8f7b8efd811 100644 --- a/src/liballoc/rc.rs +++ b/src/liballoc/rc.rs @@ -592,11 +592,9 @@ impl Rc { pub fn as_ptr(this: &Self) -> *const T { let ptr: *mut RcBox = 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 } } diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs index 289aea3afcc..27c36f4a569 100644 --- a/src/liballoc/sync.rs +++ b/src/liballoc/sync.rs @@ -591,11 +591,9 @@ impl Arc { pub fn as_ptr(this: &Self) -> *const T { let ptr: *mut ArcInner = 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 } } -- cgit 1.4.1-3-g733a5