diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs index 2bf486062fef6..caa8ffb271dd4 100644 --- a/library/core/src/ptr/mod.rs +++ b/library/core/src/ptr/mod.rs @@ -796,6 +796,17 @@ pub const fn from_mut(r: &mut T) -> *mut T { /// let slice = ptr::slice_from_raw_parts(raw_pointer, 3); /// assert_eq!(unsafe { &*slice }[2], 7); /// ``` +/// +/// You must ensure that the pointer is valid and not null before dereferencing +/// the raw slice. A slice reference must never have a null pointer, even if it's empty. +/// +/// ```rust,should_panic +/// use std::ptr; +/// let danger: *const [u8] = ptr::slice_from_raw_parts(ptr::null(), 0); +/// unsafe { +/// danger.as_ref().expect("references must not be null"); +/// } +/// ``` #[inline] #[stable(feature = "slice_from_raw_parts", since = "1.42.0")] #[rustc_const_stable(feature = "const_slice_from_raw_parts", since = "1.64.0")] @@ -805,11 +816,13 @@ pub const fn slice_from_raw_parts(data: *const T, len: usize) -> *const [T] { from_raw_parts(data.cast(), len) } +/// Forms a raw mutable slice from a pointer and a length. +/// +/// The `len` argument is the number of **elements**, not the number of bytes. +/// /// Performs the same functionality as [`slice_from_raw_parts`], except that a /// raw mutable slice is returned, as opposed to a raw immutable slice. /// -/// See the documentation of [`slice_from_raw_parts`] for more details. -/// /// This function is safe, but actually using the return value is unsafe. /// See the documentation of [`slice::from_raw_parts_mut`] for slice safety requirements. /// @@ -830,6 +843,17 @@ pub const fn slice_from_raw_parts(data: *const T, len: usize) -> *const [T] { /// /// assert_eq!(unsafe { &*slice }[2], 99); /// ``` +/// +/// You must ensure that the pointer is valid and not null before dereferencing +/// the raw slice. A slice reference must never have a null pointer, even if it's empty. +/// +/// ```rust,should_panic +/// use std::ptr; +/// let danger: *mut [u8] = ptr::slice_from_raw_parts_mut(ptr::null_mut(), 0); +/// unsafe { +/// danger.as_mut().expect("references must not be null"); +/// } +/// ``` #[inline] #[stable(feature = "slice_from_raw_parts", since = "1.42.0")] #[rustc_const_unstable(feature = "const_slice_from_raw_parts_mut", issue = "67456")]