[PATCH v2 24/28] rust: static_assert: add `static_assert!` macro

ojeda
2022-12-02T16:16:36Z

From: Miguel Ojeda <ojeda@kernel.org>

Add the `static_assert!` macro, which is a compile-time assert, similar
to the C11 `_Static_assert` and C++11 `static_assert` declarations [1,2].
Do so in a new module, called `static_assert`.

For instance:

static_assert!(42 > 24);
static_assert!(core::mem::size_of::<u8>() == 1);

const X: &[u8] = b"bar";
static_assert!(X[1] == b'a');

const fn f(x: i32) -> i32 {
x + 2
}
static_assert!(f(40) == 42);

Link: https://en.cppreference.com/w/c/language/_Static_assert [1]
Link: https://en.cppreference.com/w/cpp/language/static_assert [2]
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
rust/kernel/lib.rs | 1 +
rust/kernel/prelude.rs | 2 ++
rust/kernel/static_assert.rs | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 37 insertions(+)
create mode 100644 rust/kernel/static_assert.rs

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index d6371c9c8453..9b83ef736298 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -26,6 +26,7 @@ mod allocator;
pub mod error;
pub mod prelude;
pub mod print;
+mod static_assert;
#[doc(hidden)]
pub mod std_vendor;
pub mod str;
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index 345fc9075d1f..178fe8e6cb6d 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -19,6 +19,8 @@ pub use macros::{module, vtable};

pub use super::{dbg, pr_alert, pr_crit, pr_debug, pr_emerg, pr_err, pr_info, pr_notice, pr_warn};

+pub use super::static_assert;
+
pub use super::error::{code::*, Error, Result};

pub use super::{str::CStr, ThisModule};
diff --git a/rust/kernel/static_assert.rs b/rust/kernel/static_assert.rs
new file mode 100644
index 000000000000..3115ee0ba8e9
--- /dev/null
+++ b/rust/kernel/static_assert.rs
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Static assert.
+
+/// Static assert (i.e. compile-time assert).
+///
+/// Similar to C11 [`_Static_assert`] and C++11 [`static_assert`].
+///
+/// The feature may be added to Rust in the future: see [RFC 2790].
+///
+/// [`_Static_assert`]: https://en.cppreference.com/w/c/language/_Static_assert
+/// [`static_assert`]: https://en.cppreference.com/w/cpp/language/static_assert
+/// [RFC 2790]: https://github.com/rust-lang/rfcs/issues/2790
+///
+/// # Examples
+///
+/// ```
+/// static_assert!(42 > 24);
+/// static_assert!(core::mem::size_of::<u8>() == 1);
+///
+/// const X: &[u8] = b"bar";
+/// static_assert!(X[1] == b'a');
+///
+/// const fn f(x: i32) -> i32 {
+/// x + 2
+/// }
+/// static_assert!(f(40) == 42);
+/// ```
+#[macro_export]
+macro_rules! static_assert {
+ ($condition:expr) => {
+ const _: () = core::assert!($condition);
+ };
+}
--
2.38.1