Trait Pointer

pub trait Pointer {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

p formatting.

The Pointer trait should format its output as a memory location. This is commonly presented as hexadecimal. For more information on formatters, see the module-level documentation.

Printing of pointers is not a reliable way to discover how Rust programs are implemented. The act of reading an address changes the program itself, and may change how the data is represented in memory, and may affect which optimizations are applied to the code.

The printed pointer values are not guaranteed to be stable nor unique identifiers of objects. Rust allows moving values to different memory locations, and may reuse the same memory locations for different purposes.

There is no guarantee that the printed value can be converted back to a pointer.

Examples

Basic usage with &i32:

let x = &42;

let address = format!("{x:p}"); // this produces something like '0x7f06092ac6d0'

Implementing Pointer on a type:

use std::fmt;

struct Length(i32);

impl fmt::Pointer for Length {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // use `as` to convert to a `*const T`, which implements Pointer, which we can use

        let ptr = self as *const Self;
        fmt::Pointer::fmt(&ptr, f)
    }
}

let l = Length(42);

println!("l is in memory here: {l:p}");

let l_ptr = format!("{l:018p}");
assert_eq!(l_ptr.len(), 18);
assert_eq!(&l_ptr[..2], "0x");

Required Methods

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Implementors

impl<F> Pointer for Fwhere
    F: FnPtr,

impl<Ptr> Pointer for Pin<Ptr>where
    Ptr: Pointer,

impl<T> Pointer for *const Twhere
    T: ?Sized,

impl<T> Pointer for *mut Twhere
    T: ?Sized,

impl<T> Pointer for &Twhere
    T: ?Sized,

impl<T> Pointer for &mut Twhere
    T: ?Sized,

impl<T> Pointer for NonNull<T>where
    T: ?Sized,

impl<T> Pointer for AtomicPtr<T>Available on target_has_atomic_load_store=ptr only.

impl<T, A> Pointer for Box<T, A>where
    A: Allocator,
    T: ?Sized,

impl<T, A> Pointer for Rc<T, A>where
    A: Allocator,
    T: ?Sized,

impl<T, A> Pointer for UniqueRc<T, A>where
    A: Allocator,
    T: ?Sized,

impl<T, A> Pointer for Arc<T, A>where
    A: Allocator,
    T: ?Sized,

impl<T, A> Pointer for UniqueArc<T, A>where
    A: Allocator,
    T: ?Sized,