Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::pointer_format: pointer formatting detected

What it meansDetects pointer format as well as Debug formatting of raw pointers or function pointers or any types that have a derived Debug impl that recursively contains them. It is in the restriction group and off by default.

What you see

warning: pointer formatting detected
 --> main.rs:5:11
  |
5 | println!("{:p}", foo);
  |           ^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#pointer_format
  = note: requested on the command line with `-W clippy::pointer-format`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

The addresses are only useful in very specific contexts, and certain projects may want to keep addresses of certain data structures or functions from prying hacker eyes as an additional line of security.

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

let foo = &0_u32;
fn bar() {}
println!("{:p}", foo);
let _ = format!("{:?}", &(bar as fn()));

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
pointer_format = "warn"

In code

#![warn(clippy::pointer_format)]

One run

cargo clippy -- -W clippy::pointer-format

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Restrictiongroup

allowdefault level

nofixed by cargo clippy --fix

1.89.0added in Rust

Clippy's own documentation

What it does

Detects pointer format as well as Debug formatting of raw pointers or function pointers or any types that have a derived Debug impl that recursively contains them.

Why restrict this?

Known problems

The lint currently only looks through derived Debug implementations. Checking whether a manual implementation prints an address is left as an exercise to the next lint implementer.

Example

let foo = &0_u32;
fn bar() {}
println!("{:p}", foo);
let _ = format!("{:?}", &(bar as fn()));

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

Up next

Also worth your time

Did this answer your question?