Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
1// SPDX-License-Identifier: GPL-2.0
2
3//! Build-time assert.
4
5/// Fails the build if the code path calling `build_error!` can possibly be executed.
6///
7/// If the macro is executed in const context, `build_error!` will panic.
8/// If the compiler or optimizer cannot guarantee that `build_error!` can never
9/// be called, a build error will be triggered.
10///
11/// # Examples
12///
13/// ```
14/// # use kernel::build_error;
15/// #[inline]
16/// fn foo(a: usize) -> usize {
17/// a.checked_add(1).unwrap_or_else(|| build_error!("overflow"))
18/// }
19///
20/// assert_eq!(foo(usize::MAX - 1), usize::MAX); // OK.
21/// // foo(usize::MAX); // Fails to compile.
22/// ```
23#[macro_export]
24macro_rules! build_error {
25 () => {{
26 $crate::build_error("")
27 }};
28 ($msg:expr) => {{
29 $crate::build_error($msg)
30 }};
31}
32
33/// Asserts that a boolean expression is `true` at compile time.
34///
35/// If the condition is evaluated to `false` in const context, `build_assert!`
36/// will panic. If the compiler or optimizer cannot guarantee the condition will
37/// be evaluated to `true`, a build error will be triggered.
38///
39/// [`static_assert!`] should be preferred to `build_assert!` whenever possible.
40///
41/// # Examples
42///
43/// These examples show that different types of [`assert!`] will trigger errors
44/// at different stage of compilation. It is preferred to err as early as
45/// possible, so [`static_assert!`] should be used whenever possible.
46/// ```ignore
47/// fn foo() {
48/// static_assert!(1 > 1); // Compile-time error
49/// build_assert!(1 > 1); // Build-time error
50/// assert!(1 > 1); // Run-time error
51/// }
52/// ```
53///
54/// When the condition refers to generic parameters or parameters of an inline function,
55/// [`static_assert!`] cannot be used. Use `build_assert!` in this scenario.
56/// ```
57/// fn foo<const N: usize>() {
58/// // `static_assert!(N > 1);` is not allowed
59/// build_assert!(N > 1); // Build-time check
60/// assert!(N > 1); // Run-time check
61/// }
62///
63/// #[inline]
64/// fn bar(n: usize) {
65/// // `static_assert!(n > 1);` is not allowed
66/// build_assert!(n > 1); // Build-time check
67/// assert!(n > 1); // Run-time check
68/// }
69/// ```
70#[macro_export]
71macro_rules! build_assert {
72 ($cond:expr $(,)?) => {{
73 if !$cond {
74 $crate::build_error(concat!("assertion failed: ", stringify!($cond)));
75 }
76 }};
77 ($cond:expr, $msg:expr) => {{
78 if !$cond {
79 $crate::build_error($msg);
80 }
81 }};
82}