pointers.md

Representation of reference and pointer types

Terminology

Reference types are types of the form &T or &mut T.

Raw pointer types are types of the form *const T or *mut T.

Representation

The alignment of reference and raw pointer types is the word size.

The sizes of &T, &mut T, *const T and *mut T are the same, and are at least one word.

• If T is a trait, then the size of &T is two words.
• If T is a sized type then the size of &T is one word.
• The size of &[T] is two words.

Note that we do not make any guarantees about the sizes of multi-trait objects &(dyn T + U)or references to dynamically sized types.

Notes

The representations of &T and &mut T are the same.

The representation of &T when T is a trait is the same as that of:

#[repr(C)]
struct DynObject {
  data: &u8,
  vtable: &u8,
}

The representation of &[T] is the same as that of:

#[repr(C)]
struct Slice<T> {
  ptr: &T,
  len: usize,
}