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authorGary Guo <gary@garyguo.net>2022-11-10 19:41:37 +0300
committerMiguel Ojeda <ojeda@kernel.org>2022-12-04 03:59:16 +0300
commitecaa6ddff2fd843c0236a931bcc62bf239956617 (patch)
treee7a1b32960bd4ec652dd2e8dc34e60e9d62d289d /rust/build_error.rs
parentef9e37973c3a50497c943e70d577dad10a8e41f2 (diff)
downloadlinux-ecaa6ddff2fd843c0236a931bcc62bf239956617.tar.xz
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>
Diffstat (limited to 'rust/build_error.rs')
-rw-r--r--rust/build_error.rs31
1 files changed, 31 insertions, 0 deletions
diff --git a/rust/build_error.rs b/rust/build_error.rs
new file mode 100644
index 000000000000..fa24eeef9929
--- /dev/null
+++ b/rust/build_error.rs
@@ -0,0 +1,31 @@
+// 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);
+}