linux-stable/rust/build_error.rs
Gary Guo ecaa6ddff2 rust: add build_error crate
The `build_error` crate provides a function `build_error` which
will panic at compile-time if executed in const context and,
by default, will cause a build error if not executed at compile
time and the optimizer does not optimise away the call.

The `CONFIG_RUST_BUILD_ASSERT_ALLOW` kernel option allows to
relax the default build failure and convert it to a runtime
check. If the runtime check fails, `panic!` will be called.

Its functionality will be exposed to users as a couple macros in
the `kernel` crate in the following patch, thus some documentation
here refers to them for simplicity.

Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2022-12-04 01:59:16 +01:00

31 lines
1.3 KiB
Rust

// SPDX-License-Identifier: GPL-2.0
//! Build-time error.
//!
//! This crate provides a [const function][const-functions] `build_error`, which will panic in
//! compile-time if executed in [const context][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][const-functions], but those
//! functions could still be called in the runtime).
//!
//! For details on constant evaluation in Rust, please see the [Reference][const-eval].
//!
//! [const-eval]: https://doc.rust-lang.org/reference/const_eval.html
//! [const-functions]: https://doc.rust-lang.org/reference/const_eval.html#const-functions
//! [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
#![no_std]
/// Panics if executed in [const context][const-context], or triggers a build error if not.
///
/// [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
#[inline(never)]
#[cold]
#[export_name = "rust_build_error"]
#[track_caller]
pub const fn build_error(msg: &'static str) -> ! {
panic!("{}", msg);
}