[PATCH RESEND] rust: replace `build_assert!` with `const_assert!`

[PATCH RESEND] rust: replace `build_assert!` with `const_assert!`

[Mohamad Alsadhan]

Several Rust assertions currently use the `build_assert!` macro
despite their conditions only depending on type parameters or const
generics, not runtime values.

Replace these with the more appropriate `const_assert!` macro which
should trigger earlier in the compilation pipeline. This is possible
since commit 560a7a9b9 ("rust: add `const_assert!` macro").

These changes were identified by my PR to klint (see link), which
added a new lint that suggests to use stronger build-time assertion
forms when possible.

No functional change intended.

Link: https://github.com/Rust-for-Linux/klint/pull/14
Acked-by: Tamir Duberstein <tamird@kernel.org>
Signed-off-by: Mohamad Alsadhan <mo@sdhn.cc>
---
 rust/kernel/dma.rs            | 4 ++--
 rust/kernel/i2c.rs            | 2 +-
 rust/kernel/list/arc.rs       | 2 +-
 rust/kernel/sync/locked_by.rs | 8 ++++----
 rust/kernel/xarray.rs         | 4 ++--
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
index 909d56fd5..deacfc719 100644
--- a/rust/kernel/dma.rs
+++ b/rust/kernel/dma.rs
@@ -5,7 +5,7 @@
 //! C header: [`include/linux/dma-mapping.h`](srctree/include/linux/dma-mapping.h)
 
 use crate::{
-    bindings, build_assert, device,
+    bindings, device,
     device::{Bound, Core},
     error::{to_result, Result},
     prelude::*,
@@ -401,7 +401,7 @@ pub fn alloc_attrs(
         gfp_flags: kernel::alloc::Flags,
         dma_attrs: Attrs,
     ) -> Result<CoherentAllocation<T>> {
-        build_assert!(
+        const_assert!(
             core::mem::size_of::<T>() > 0,
             "It doesn't make sense for the allocated type to be a ZST"
         );
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 7b908f0c5..55b763189 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -110,7 +110,7 @@ unsafe fn register(
         name: &'static CStr,
         module: &'static ThisModule,
     ) -> Result {
-        build_assert!(
+        const_assert!(
             T::ACPI_ID_TABLE.is_some() || T::OF_ID_TABLE.is_some() || T::I2C_ID_TABLE.is_some(),
             "At least one of ACPI/OF/Legacy tables must be present when registering an i2c driver"
         );
diff --git a/rust/kernel/list/arc.rs b/rust/kernel/list/arc.rs
index e10824239..b57cec64f 100644
--- a/rust/kernel/list/arc.rs
+++ b/rust/kernel/list/arc.rs
@@ -252,7 +252,7 @@ pub fn pair_from_pin_unique<const ID2: u64>(
     where
         T: ListArcSafe<ID2>,
     {
-        build_assert!(ID != ID2);
+        const_assert!(ID != ID2);
 
         // SAFETY: We have a `UniqueArc`, so there is no `ListArc`.
         unsafe { <T as ListArcSafe<ID>>::on_create_list_arc_from_unique(unique.as_mut()) };
diff --git a/rust/kernel/sync/locked_by.rs b/rust/kernel/sync/locked_by.rs
index 61f100a45..5d043e661 100644
--- a/rust/kernel/sync/locked_by.rs
+++ b/rust/kernel/sync/locked_by.rs
@@ -3,7 +3,7 @@
 //! A wrapper for data protected by a lock that does not wrap it.
 
 use super::{lock::Backend, lock::Lock};
-use crate::build_assert;
+use crate::const_assert;
 use core::{cell::UnsafeCell, mem::size_of, ptr};
 
 /// Allows access to some data to be serialised by a lock that does not wrap it.
@@ -100,7 +100,7 @@ impl<T, U> LockedBy<T, U> {
     /// memory location*, the data becomes accessible again: none of this affects memory safety
     /// because in any case at most one thread (or CPU) can access the protected data at a time.
     pub fn new<B: Backend>(owner: &Lock<U, B>, data: T) -> Self {
-        build_assert!(
+        const_assert!(
             size_of::<Lock<U, B>>() > 0,
             "The lock type cannot be a ZST because it may be impossible to distinguish instances"
         );
@@ -126,7 +126,7 @@ pub fn access<'a>(&'a self, owner: &'a U) -> &'a T
     where
         T: Sync,
     {
-        build_assert!(
+        const_assert!(
             size_of::<U>() > 0,
             "`U` cannot be a ZST because `owner` wouldn't be unique"
         );
@@ -155,7 +155,7 @@ pub fn access<'a>(&'a self, owner: &'a U) -> &'a T
     /// Panics if `owner` is different from the data protected by the lock used in
     /// [`new`](LockedBy::new).
     pub fn access_mut<'a>(&'a self, owner: &'a mut U) -> &'a mut T {
-        build_assert!(
+        const_assert!(
             size_of::<U>() > 0,
             "`U` cannot be a ZST because `owner` wouldn't be unique"
         );
diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
index 46e5f4322..d4b3eac34 100644
--- a/rust/kernel/xarray.rs
+++ b/rust/kernel/xarray.rs
@@ -5,7 +5,7 @@
 //! C header: [`include/linux/xarray.h`](srctree/include/linux/xarray.h)
 
 use crate::{
-    alloc, bindings, build_assert,
+    alloc, bindings, const_assert,
     error::{Error, Result},
     ffi::c_void,
     types::{ForeignOwnable, NotThreadSafe, Opaque},
@@ -231,7 +231,7 @@ pub fn store(
         value: T,
         gfp: alloc::Flags,
     ) -> Result<Option<T>, StoreError<T>> {
-        build_assert!(
+        const_assert!(
             T::FOREIGN_ALIGN >= 4,
             "pointers stored in XArray must be 4-byte aligned"
         );
-- 
2.54.0

Re: [PATCH RESEND] rust: replace `build_assert!` with `const_assert!`

[kernel test robot]

Hi Mohamad,

kernel test robot noticed the following build errors:

[auto build test ERROR on rust/xarray-next]
[cannot apply to rust/rust-next driver-core/driver-core-testing driver-core/driver-core-next driver-core/driver-core-linus tip/locking/core linus/master v7.1-rc5 next-20260525]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Mohamad-Alsadhan/rust-replace-build_assert-with-const_assert/20260523-202931
base:   https://github.com/Rust-for-Linux/linux xarray-next
patch link:    https://lore.kernel.org/r/20260523122759.30317-1-mo%40sdhn.cc
patch subject: [PATCH RESEND] rust: replace `build_assert!` with `const_assert!`
config: x86_64-randconfig-161-20260526 (https://download.01.org/0day-ci/archive/20260526/202605261249.YsIyj5Ye-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
smatch: v0.5.0-9185-gbcc58b9c
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260526/202605261249.YsIyj5Ye-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605261249.YsIyj5Ye-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

>> error[E0432]: unresolved import `crate::const_assert`
   --> rust/kernel/sync/locked_by.rs:6:5
   |
   6 | use crate::const_assert;
   |     ^^^^^^^------------
   |     |      |
   |     |      help: a similar name exists in the module: `kunit_assert`
   |     no `const_assert` in the root
--
>> error[E0432]: unresolved import `crate::const_assert`
   --> rust/kernel/xarray.rs:8:22
   |
   8 |     alloc, bindings, const_assert,
   |                      ^^^^^^^^^^^^
   |                      |
   |                      no `const_assert` in the root
   |                      help: a similar name exists in the module: `kunit_assert`
--
>> error: cannot find macro `const_assert` in this scope
   --> rust/kernel/list/arc.rs:254:9
   |
   254 |         const_assert!(ID != ID2);
   |         ^^^^^^^^^^^^
--
>> error: cannot find macro `const_assert` in this scope
   --> rust/kernel/i2c.rs:105:9
   |
   105 |         const_assert!(
   |         ^^^^^^^^^^^^
--
>> error: cannot find macro `const_assert` in this scope
   --> rust/kernel/dma.rs:386:9
   |
   386 |         const_assert!(
   |         ^^^^^^^^^^^^
--
>> warning: unused import: `mem::size_of`
   --> rust/kernel/sync/locked_by.rs:7:30
   |
   7 | use core::{cell::UnsafeCell, mem::size_of, ptr};
   |                              ^^^^^^^^^^^^
   |
   = note: `#[warn(unused_imports)]` on by default

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