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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>
32 lines
1.3 KiB
Rust
32 lines
1.3 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Build-time error.
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//!
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//! This crate provides a [const function][const-functions] `build_error`, which will panic in
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//! compile-time if executed in [const context][const-context], and will cause a build error
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//! if not executed at compile time and the optimizer does not optimise away the call.
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//!
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//! It is used by `build_assert!` in the kernel crate, allowing checking of
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//! conditions that could be checked statically, but could not be enforced in
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//! Rust yet (e.g. perform some checks in [const functions][const-functions], but those
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//! functions could still be called in the runtime).
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//!
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//! For details on constant evaluation in Rust, please see the [Reference][const-eval].
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//!
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//! [const-eval]: https://doc.rust-lang.org/reference/const_eval.html
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//! [const-functions]: https://doc.rust-lang.org/reference/const_eval.html#const-functions
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//! [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
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#![no_std]
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/// Panics if executed in [const context][const-context], or triggers a build error if not.
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///
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/// [const-context]: https://doc.rust-lang.org/reference/const_eval.html#const-context
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#[inline(never)]
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#[cold]
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#[export_name = "rust_build_error"]
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#[track_caller]
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pub const fn build_error(msg: &'static str) -> ! {
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panic!("{}", msg);
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}
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