rust/build_error.rs

// SPDX-License-Identifier: GPL-2.0

//! Build-time error.
//!
//! This crate provides a function `build_error`, which will panic in
//! compile-time if executed in const context, and will cause a build error
//! if not executed at compile time and the optimizer does not optimise away the
//! call.
//!
//! It is used by `build_assert!` in the kernel crate, allowing checking of
//! conditions that could be checked statically, but could not be enforced in
//! Rust yet (e.g. perform some checks in const functions, but those
//! functions could still be called in the runtime).

#![no_std]
#![feature(const_panic, core_panic)]

/// Panics if executed in const context, or triggers a build error if not.
#[inline(never)]
#[cold]
#[no_mangle]
#[track_caller]
pub const fn build_error(msg: &'static str) -> ! {
    // Could also be `panic!(msg)` to avoid using unstable feature `core_panic`,
    // but it is not allowed in Rust 2021, while `panic!("{}", msg)` could not
    // yet be used in const context.
    core::panicking::panic(msg);
}

#[cfg(CONFIG_RUST_BUILD_ASSERT_WARN)]
#[link_section = ".gnu.warning.build_error"]
#[used]
static BUILD_ERROR_WARNING: [u8; 45] = *b"call to build_error present after compilation";