Clippy lint · Correctness · checked with Clippy 0.1.99

clippy::zst_offset: offset calculation on zero-sized value

What it meansChecks for offset(_), wrapping_{add, sub}, etc. on raw pointers to zero-sized types It is in the correctness group and denied by default (the build fails).

What you see

error: offset calculation on zero-sized value
 --> main.rs:3:10
  |
3 | unsafe { (&() as *const ()).offset(1) };
  |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#zst_offset
  = note: `#[deny(clippy::zst_offset)]` on by default

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?

This is a no-op, and likely unintended

Code that is almost certainly wrong. Denied by default: the build fails until you fix it or allow it.

How to fix it

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

Flagged

unsafe { (&() as *const ()).offset(1) };

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

On one item

#[allow(clippy::zst_offset)]
fn my_function() { /* ... */ }

Whole crate (Cargo.toml)

[lints.clippy]
zst_offset = "allow"

One run

cargo clippy -- -A clippy::zst-offset

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.

Correctnessgroup

denydefault level

nofixed by cargo clippy --fix

1.41.0added in Rust

Clippy's own documentation

What it does

Checks for offset(_), wrapping_{add, sub}, etc. on raw pointers to zero-sized types

Why is this bad?

This is a no-op, and likely unintended

Example

unsafe { (&() as *const ()).offset(1) };

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

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