diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs index b83a18027193e..c80639298234e 100644 --- a/library/core/src/ptr/mod.rs +++ b/library/core/src/ptr/mod.rs @@ -2285,9 +2285,13 @@ impl fmt::Debug for F { /// `addr_of!(expr)` is equivalent to `&raw const expr`. The macro is *soft-deprecated*; /// use `&raw const` instead. /// -/// It is still an open question whether writing through an `addr_of!`-created pointer is permitted -/// or not. Until that is decided, the same rules as for shared references apply: it is UB to write -/// through a pointer created with this operation, except for bytes located inside an `UnsafeCell`. +/// It is still an open question under which conditions writing through an `addr_of!`-created +/// pointer is permitted. If the place `expr` evaluates to is based on a raw pointer, then the +/// result of `addr_of!` inherits all permissions from that raw pointer. However, if the place is +/// based on a reference, local variable, or `static`, then until all details are decided, the same +/// rules as for shared references apply: it is UB to write through a pointer created with this +/// operation, except for bytes located inside an `UnsafeCell`. Use `&raw mut` (or `addr_of_mut!`) +/// to create a raw pointer that permits mutation. /// /// Creating a reference with `&`/`&mut` is only allowed if the pointer is properly aligned /// and points to initialized data. For cases where those requirements do not hold,