diff options
| -rw-r--r-- | library/core/src/num/nonzero.rs | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/library/core/src/num/nonzero.rs b/library/core/src/num/nonzero.rs index dbce64420ac..bf7ba3222d0 100644 --- a/library/core/src/num/nonzero.rs +++ b/library/core/src/num/nonzero.rs @@ -90,6 +90,26 @@ impl_zeroable_primitive!( /// /// assert_eq!(size_of::<Option<NonZero<u32>>>(), size_of::<u32>()); /// ``` +/// +/// # Layout +/// +/// `NonZero<T>` is guaranteed to have the same layout and bit validity as `T` +/// with the exception that the all-zero bit pattern is not a valid instance. +/// `Option<NonZero<T>>` is guaranteed to be compatible with `T`, including in +/// FFI. +/// +/// Thanks to the [null pointer optimization], `NonZero<T>` and +/// `Option<NonZero<T>>` are guaranteed to have the same size and alignment: +/// +/// ``` +/// # use std::mem::{size_of, align_of}; +/// use std::num::NonZero; +/// +/// assert_eq!(size_of::<NonZero<u32>>(), size_of::<Option<NonZero<u32>>>()); +/// assert_eq!(align_of::<NonZero<u32>>(), align_of::<Option<NonZero<u32>>>()); +/// ``` +/// +/// [null pointer optimization]: crate::option#representation #[stable(feature = "generic_nonzero", since = "1.79.0")] #[repr(transparent)] #[rustc_nonnull_optimization_guaranteed] |