1 // SPDX-License-Identifier: GPL-2.0
2
3 //! Build-time error.
4 //!
5 //! This crate provides a [const function][const-functions] `build_error`, which will panic in
6 //! compile-time if executed in [const context][const-context], and will cause a build error
7 //! if not executed at compile time and the optimizer does not optimise away the call.
8 //!
9 //! It is used by `build_assert!` in the kernel crate, allowing checking of
10 //! conditions that could be checked statically, but could not be enforced in
11 //! Rust yet (e.g. perform some checks in [const functions][const-functions], but those
12 //! functions could still be called in the runtime).
13 //!
14 //! For details on constant evaluation in Rust, please see the [Reference][const-eval].
15 //!
16 //! [const-eval]: https://doc.rust-lang.org/reference/const_eval.html
17 //! [const-functions]: https://doc.rust-lang.org/reference/const_eval.html#const-functions
18 //! [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
19
20 #![no_std]
21
22 /// Panics if executed in [const context][const-context], or triggers a build error if not.
23 ///
24 /// [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
25 #[inline(never)]
26 #[cold]
27 #[export_name = "rust_build_error"]
28 #[track_caller]
29 pub const fn build_error(msg: &'static str) -> ! {
30 panic!("{}", msg);
31 }
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