1 // SPDX-License-Identifier: GPL-2.0
2 
3 //! Static assert.
4 
5 /// Static assert (i.e. compile-time assert).
6 ///
7 /// Similar to C11 [`_Static_assert`] and C++11 [`static_assert`].
8 ///
9 /// An optional panic message can be supplied after the expression.
10 /// Currently only a string literal without formatting is supported
11 /// due to constness limitations of the [`assert!`] macro.
12 ///
13 /// The feature may be added to Rust in the future: see [RFC 2790].
14 ///
15 /// [`_Static_assert`]: https://en.cppreference.com/w/c/language/_Static_assert
16 /// [`static_assert`]: https://en.cppreference.com/w/cpp/language/static_assert
17 /// [RFC 2790]: https://github.com/rust-lang/rfcs/issues/2790
18 ///
19 /// # Examples
20 ///
21 /// ```
22 /// static_assert!(42 > 24);
23 /// static_assert!(core::mem::size_of::<u8>() == 1);
24 ///
25 /// const X: &[u8] = b"bar";
26 /// static_assert!(X[1] == b'a');
27 ///
28 /// const fn f(x: i32) -> i32 {
29 ///     x + 2
30 /// }
31 /// static_assert!(f(40) == 42);
32 /// static_assert!(f(40) == 42, "f(x) must add 2 to the given input.");
33 /// ```
34 #[macro_export]
35 macro_rules! static_assert {
36     ($condition:expr $(,$arg:literal)?) => {
37         const _: () = ::core::assert!($condition $(,$arg)?);
38     };
39 }
40