Clippy lints / Pedantic
Clippy lint · Pedantic · checked with Clippy 0.1.99
clippy::no_mangle_with_rust_abi: `#[no_mangle]` set on a function with the default (`Rust`) ABI
What it meansChecks for Rust ABI functions with the #[no_mangle] attribute. It is in the pedantic group and off by default.
What you see
warning: `#[no_mangle]` set on a function with the default (`Rust`) ABI --> main.rs:4:2 | 4 | fn example(arg_one: u32, arg_two: usize) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#no_mangle_with_rust_abi = note: `-W clippy::no-mangle-with-rust-abi` implied by `-W clippy::pedantic` help: set an ABI | 4 | extern "C" fn example(arg_one: u32, arg_two: usize) {} | ++++++++++ help: or explicitly set the default | 4 | extern "Rust" fn example(arg_one: u32, arg_two: usize) {} | +++++++++++++
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 Rust ABI is not stable, but in many simple cases matches enough with the C ABI that it is possible to forget to add extern "C" to a function called from C. Changes to the Rust ABI can break this at any point.
Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.
How to fix it
Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:
Flagged
#[no_mangle]
fn example(arg_one: u32, arg_two: usize) {}
Write this instead
#[no_mangle]
extern "C" fn example(arg_one: u32, arg_two: usize) {}
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]
no_mangle_with_rust_abi = "warn"In code
#![warn(clippy::no_mangle_with_rust_abi)]One run
cargo clippy -- -W clippy::no-mangle-with-rust-abiThe [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.
Clippy's own documentation
What it does
Checks for Rust ABI functions with the #[no_mangle] attribute.
Why is this bad?
The Rust ABI is not stable, but in many simple cases matches
enough with the C ABI that it is possible to forget to add
extern "C" to a function called from C. Changes to the
Rust ABI can break this at any point.
Example
#[no_mangle]
fn example(arg_one: u32, arg_two: usize) {}
Use instead:
#[no_mangle]
extern "C" fn example(arg_one: u32, arg_two: usize) {}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
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All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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