diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs index 63e42a8784c6a..d71079dd09c59 100644 --- a/library/core/src/ptr/mod.rs +++ b/library/core/src/ptr/mod.rs @@ -1999,9 +1999,18 @@ impl fmt::Debug for F { /// as all other references. This macro can create a raw pointer *without* creating /// a reference first. /// -/// Note, however, that the `expr` in `addr_of!(expr)` is still subject to all -/// the usual rules. In particular, `addr_of!(*ptr::null())` is Undefined -/// Behavior because it dereferences a null pointer. +/// The `expr` in `addr_of!(expr)` is evaluated as a place expression, but never loads +/// from the place or requires the place to be dereferenceable. This means that +/// `addr_of!(*ptr)` is defined behavior even if `ptr` is null, dangling, or misaligned. +/// Note however that `addr_of!((*ptr).field)` still requires the projection to +/// `field` to be in-bounds, using the same rules as [`offset`]. +/// +/// Note that `Deref`/`Index` coercions (and their mutable counterparts) are applied inside +/// `addr_of!` like everywhere else, in which case a reference is created to call `Deref::deref` or +/// `Index::index`, respectively. The statements above only apply when no such coercions are +/// applied. +/// +/// [`offset`]: pointer::offset /// /// # Example /// @@ -2039,9 +2048,18 @@ pub macro addr_of($place:expr) { /// as all other references. This macro can create a raw pointer *without* creating /// a reference first. /// -/// Note, however, that the `expr` in `addr_of_mut!(expr)` is still subject to all -/// the usual rules. In particular, `addr_of_mut!(*ptr::null_mut())` is Undefined -/// Behavior because it dereferences a null pointer. +/// The `expr` in `addr_of_mut!(expr)` is evaluated as a place expression, but never loads +/// from the place or requires the place to be dereferenceable. This means that +/// `addr_of_mut!(*ptr)` is defined behavior even if `ptr` is null, dangling, or misaligned. +/// Note however that `addr_of_mut!((*ptr).field)` still requires the projection to +/// `field` to be in-bounds, using the same rules as [`offset`]. +/// +/// Note that `Deref`/`Index` coercions (and their mutable counterparts) are applied inside +/// `addr_of_mut!` like everywhere else, in which case a reference is created to call `Deref::deref` +/// or `Index::index`, respectively. The statements above only apply when no such coercions are +/// applied. +/// +/// [`offset`]: pointer::offset /// /// # Examples ///