From: José Expósito <jose.exposito89@gmail.com>

Add a couple of Rust const functions and macros to allow to develop
KUnit tests without relying on generated C code:

 - The `kunit_unsafe_test_suite!` Rust macro is similar to the
   `kunit_test_suite` C macro. It requires a NULL-terminated array of
   test cases (see below).
 - The `kunit_case` Rust function is similar to the `KUNIT_CASE` C macro.
   It generates as case from the name and function.
 - The `kunit_case_null` Rust function generates a NULL test case, which
   is to be used as delimiter in `kunit_test_suite!`.

While these functions and macros can be used on their own, a future
patch will introduce another macro to create KUnit tests using a
user-space like syntax.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Co-developed-by: Matt Gilbride <mattgilbride@google.com>
Signed-off-by: Matt Gilbride <mattgilbride@google.com>
Co-developed-by: David Gow <davidgow@google.com>
Signed-off-by: David Gow <davidgow@google.com>
---

Changes since v3:
https://lore.kernel.org/linux-kselftest/20241030045719.3085147-4-davidgow@google.com/
- The kunit_unsafe_test_suite!() macro now panic!s if the suite name is
  too long, triggering a compile error. (Thanks, Alice!)

Changes since v2:
https://lore.kernel.org/linux-kselftest/20241029092422.2884505-2-davidgow@google.com/
- The kunit_unsafe_test_suite!() macro will truncate the name of the
  suite if it is too long. (Thanks Alice!)
- We no longer needlessly use UnsafeCell<> in
  kunit_unsafe_test_suite!(). (Thanks Alice!)

Changes since v1:
https://lore.kernel.org/lkml/20230720-rustbind-v1-1-c80db349e3b5@google.com/
- Rebase on top of rust-next
- As a result, KUnit attributes are new set. These are hardcoded to the
  defaults of "normal" speed and no module name.
- Split the kunit_case!() macro into two const functions, kunit_case()
  and kunit_case_null() (for the NULL terminator).

---
 rust/kernel/kunit.rs | 112 +++++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs   |   1 +
 2 files changed, 113 insertions(+)

diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 824da0e9738a..85bc1faff0d5 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -161,3 +161,115 @@ macro_rules! kunit_assert_eq {
         $crate::kunit_assert!($name, $file, $diff, $left == $right);
     }};
 }
+
+/// Represents an individual test case.
+///
+/// The test case should have the signature
+/// `unsafe extern "C" fn test_case(test: *mut crate::bindings::kunit)`.
+///
+/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases.
+/// Use `kunit_case_null` to generate such a delimeter.
+const fn kunit_case(name: &'static kernel::str::CStr, run_case: unsafe extern "C" fn(*mut kernel::bindings::kunit)) -> kernel::bindings::kunit_case {
+    kernel::bindings::kunit_case {
+        run_case: Some(run_case),
+        name: name.as_char_ptr(),
+        attr: kernel::bindings::kunit_attributes {
+            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
+        },
+        generate_params: None,
+        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
+        module_name: core::ptr::null_mut(),
+        log: core::ptr::null_mut(),
+    }
+}
+
+/// Represents the NULL test case delimiter.
+///
+/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases. This
+/// function retuns such a delimiter.
+const fn kunit_case_null() -> kernel::bindings::kunit_case {
+    kernel::bindings::kunit_case {
+        run_case: None,
+        name: core::ptr::null_mut(),
+        generate_params: None,
+        attr: kernel::bindings::kunit_attributes {
+            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
+        },
+        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
+        module_name: core::ptr::null_mut(),
+        log: core::ptr::null_mut(),
+    }
+}
+
+
+/// Registers a KUnit test suite.
+///
+/// # Safety
+///
+/// `test_cases` must be a NULL terminated array of test cases.
+///
+/// # Examples
+///
+/// ```ignore
+/// unsafe extern "C" fn test_fn(_test: *mut crate::bindings::kunit) {
+///     let actual = 1 + 1;
+///     let expected = 2;
+///     assert_eq!(actual, expected);
+/// }
+///
+/// static mut KUNIT_TEST_CASE: crate::bindings::kunit_case = crate::kunit_case(name, test_fn);
+/// static mut KUNIT_NULL_CASE: crate::bindings::kunit_case = crate::kunit_case_null();
+/// static mut KUNIT_TEST_CASES: &mut[crate::bindings::kunit_case] = unsafe {
+///     &mut[KUNIT_TEST_CASE, KUNIT_NULL_CASE]
+/// };
+/// crate::kunit_unsafe_test_suite!(suite_name, KUNIT_TEST_CASES);
+/// ```
+#[macro_export]
+macro_rules! kunit_unsafe_test_suite {
+    ($name:ident, $test_cases:ident) => {
+        const _: () = {
+            static KUNIT_TEST_SUITE_NAME: [i8; 256] = {
+                let name_u8 = core::stringify!($name).as_bytes();
+                let mut ret = [0; 256];
+
+                if name_u8.len() > 255 {
+                    panic!(concat!("The test suite name `", core::stringify!($name), "` exceeds the maximum length of 255 bytes."));
+                }
+
+                let mut i = 0;
+                while i < name_u8.len() {
+                    ret[i] = name_u8[i] as i8;
+                    i += 1;
+                }
+
+                ret
+            };
+
+            static mut KUNIT_TEST_SUITE: $crate::bindings::kunit_suite =
+                $crate::bindings::kunit_suite {
+                    name: KUNIT_TEST_SUITE_NAME,
+                    // SAFETY: User is expected to pass a correct `test_cases`, hence this macro
+                    // named 'unsafe'.
+                    test_cases: unsafe { $test_cases.as_mut_ptr() },
+                    suite_init: None,
+                    suite_exit: None,
+                    init: None,
+                    exit: None,
+                    attr: $crate::bindings::kunit_attributes {
+                        speed: $crate::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
+                    },
+                    status_comment: [0; 256usize],
+                    debugfs: core::ptr::null_mut(),
+                    log: core::ptr::null_mut(),
+                    suite_init_err: 0,
+                    is_init: false,
+                };
+
+            #[used]
+            #[link_section = ".kunit_test_suites"]
+            static mut KUNIT_TEST_SUITE_ENTRY: *const $crate::bindings::kunit_suite =
+                // SAFETY: `KUNIT_TEST_SUITE` is static.
+                unsafe { core::ptr::addr_of_mut!(KUNIT_TEST_SUITE) };
+        };
+    };
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index b62451f64f6e..d662aa37070f 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -18,6 +18,7 @@
 #![feature(inline_const)]
 #![feature(lint_reasons)]
 #![feature(unsize)]
+#![feature(const_mut_refs)]
 
 // Ensure conditional compilation based on the kernel configuration works;
 // otherwise we may silently break things like initcall handling.
-- 
2.47.0.199.ga7371fff76-goog

On Fri, Nov 01, 2024 at 02:45:00PM +0800, David Gow wrote:
> From: José Expósito <jose.exposito89@gmail.com>
> 
> Add a couple of Rust const functions and macros to allow to develop
> KUnit tests without relying on generated C code:
> 
>  - The `kunit_unsafe_test_suite!` Rust macro is similar to the
>    `kunit_test_suite` C macro. It requires a NULL-terminated array of
>    test cases (see below).
>  - The `kunit_case` Rust function is similar to the `KUNIT_CASE` C macro.
>    It generates as case from the name and function.
>  - The `kunit_case_null` Rust function generates a NULL test case, which
>    is to be used as delimiter in `kunit_test_suite!`.
> 
> While these functions and macros can be used on their own, a future
> patch will introduce another macro to create KUnit tests using a
> user-space like syntax.
> 
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> Co-developed-by: Matt Gilbride <mattgilbride@google.com>
> Signed-off-by: Matt Gilbride <mattgilbride@google.com>
> Co-developed-by: David Gow <davidgow@google.com>
> Signed-off-by: David Gow <davidgow@google.com>
> ---
> 
> Changes since v3:
> https://lore.kernel.org/linux-kselftest/20241030045719.3085147-4-davidgow@google.com/
> - The kunit_unsafe_test_suite!() macro now panic!s if the suite name is
>   too long, triggering a compile error. (Thanks, Alice!)
> 
> Changes since v2:
> https://lore.kernel.org/linux-kselftest/20241029092422.2884505-2-davidgow@google.com/
> - The kunit_unsafe_test_suite!() macro will truncate the name of the
>   suite if it is too long. (Thanks Alice!)
> - We no longer needlessly use UnsafeCell<> in
>   kunit_unsafe_test_suite!(). (Thanks Alice!)
> 
> Changes since v1:
> https://lore.kernel.org/lkml/20230720-rustbind-v1-1-c80db349e3b5@google.com/
> - Rebase on top of rust-next
> - As a result, KUnit attributes are new set. These are hardcoded to the
>   defaults of "normal" speed and no module name.
> - Split the kunit_case!() macro into two const functions, kunit_case()
>   and kunit_case_null() (for the NULL terminator).
> 
> ---
>  rust/kernel/kunit.rs | 112 +++++++++++++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs   |   1 +
>  2 files changed, 113 insertions(+)
> 
> diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> index 824da0e9738a..85bc1faff0d5 100644
> --- a/rust/kernel/kunit.rs
> +++ b/rust/kernel/kunit.rs
> @@ -161,3 +161,115 @@ macro_rules! kunit_assert_eq {
>          $crate::kunit_assert!($name, $file, $diff, $left == $right);
>      }};
>  }
> +
> +/// Represents an individual test case.
> +///
> +/// The test case should have the signature
> +/// `unsafe extern "C" fn test_case(test: *mut crate::bindings::kunit)`.
> +///
> +/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases.
> +/// Use `kunit_case_null` to generate such a delimeter.
> +const fn kunit_case(name: &'static kernel::str::CStr, run_case: unsafe extern "C" fn(*mut kernel::bindings::kunit)) -> kernel::bindings::kunit_case {
> +    kernel::bindings::kunit_case {
> +        run_case: Some(run_case),
> +        name: name.as_char_ptr(),
> +        attr: kernel::bindings::kunit_attributes {
> +            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> +        },
> +        generate_params: None,
> +        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
> +        module_name: core::ptr::null_mut(),
> +        log: core::ptr::null_mut(),
> +    }
> +}
> +
> +/// Represents the NULL test case delimiter.
> +///
> +/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases. This
> +/// function retuns such a delimiter.
> +const fn kunit_case_null() -> kernel::bindings::kunit_case {
> +    kernel::bindings::kunit_case {
> +        run_case: None,
> +        name: core::ptr::null_mut(),
> +        generate_params: None,
> +        attr: kernel::bindings::kunit_attributes {
> +            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> +        },
> +        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
> +        module_name: core::ptr::null_mut(),
> +        log: core::ptr::null_mut(),
> +    }
> +}
> +
> +
> +/// Registers a KUnit test suite.
> +///
> +/// # Safety
> +///
> +/// `test_cases` must be a NULL terminated array of test cases.
> +///
> +/// # Examples
> +///
> +/// ```ignore
> +/// unsafe extern "C" fn test_fn(_test: *mut crate::bindings::kunit) {
> +///     let actual = 1 + 1;
> +///     let expected = 2;
> +///     assert_eq!(actual, expected);
> +/// }
> +///
> +/// static mut KUNIT_TEST_CASE: crate::bindings::kunit_case = crate::kunit_case(name, test_fn);
> +/// static mut KUNIT_NULL_CASE: crate::bindings::kunit_case = crate::kunit_case_null();
> +/// static mut KUNIT_TEST_CASES: &mut[crate::bindings::kunit_case] = unsafe {
> +///     &mut[KUNIT_TEST_CASE, KUNIT_NULL_CASE]
> +/// };
> +/// crate::kunit_unsafe_test_suite!(suite_name, KUNIT_TEST_CASES);
> +/// ```
> +#[macro_export]
> +macro_rules! kunit_unsafe_test_suite {
> +    ($name:ident, $test_cases:ident) => {
> +        const _: () = {
> +            static KUNIT_TEST_SUITE_NAME: [i8; 256] = {
> +                let name_u8 = core::stringify!($name).as_bytes();
> +                let mut ret = [0; 256];
> +
> +                if name_u8.len() > 255 {
> +                    panic!(concat!("The test suite name `", core::stringify!($name), "` exceeds the maximum length of 255 bytes."));
> +                }
> +
> +                let mut i = 0;
> +                while i < name_u8.len() {
> +                    ret[i] = name_u8[i] as i8;
> +                    i += 1;
> +                }
> +
> +                ret
> +            };
> +
> +            static mut KUNIT_TEST_SUITE: $crate::bindings::kunit_suite =
> +                $crate::bindings::kunit_suite {
> +                    name: KUNIT_TEST_SUITE_NAME,
> +                    // SAFETY: User is expected to pass a correct `test_cases`, hence this macro
> +                    // named 'unsafe'.
> +                    test_cases: unsafe { $test_cases.as_mut_ptr() },
> +                    suite_init: None,
> +                    suite_exit: None,
> +                    init: None,
> +                    exit: None,
> +                    attr: $crate::bindings::kunit_attributes {
> +                        speed: $crate::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> +                    },
> +                    status_comment: [0; 256usize],
> +                    debugfs: core::ptr::null_mut(),
> +                    log: core::ptr::null_mut(),
> +                    suite_init_err: 0,
> +                    is_init: false,
> +                };
> +
> +            #[used]
> +            #[link_section = ".kunit_test_suites"]
> +            static mut KUNIT_TEST_SUITE_ENTRY: *const $crate::bindings::kunit_suite =
> +                // SAFETY: `KUNIT_TEST_SUITE` is static.
> +                unsafe { core::ptr::addr_of_mut!(KUNIT_TEST_SUITE) };

FYI, `addr_of` and `addr_of_mut` is safe now on statics since 1.82:

	https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html#safely-addressing-unsafe-statics

We need a `#[allow(unused_unsafe)]` here to avoid the unused unsafe
warning.

Regards,
Boqun

> +        };
> +    };
> +}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index b62451f64f6e..d662aa37070f 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -18,6 +18,7 @@
>  #![feature(inline_const)]
>  #![feature(lint_reasons)]
>  #![feature(unsize)]
> +#![feature(const_mut_refs)]
>  
>  // Ensure conditional compilation based on the kernel configuration works;
>  // otherwise we may silently break things like initcall handling.
> -- 
> 2.47.0.199.ga7371fff76-goog
> 
> 

On Sat, 2 Nov 2024 at 01:47, Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Fri, Nov 01, 2024 at 02:45:00PM +0800, David Gow wrote:
> > From: José Expósito <jose.exposito89@gmail.com>
> >
> > Add a couple of Rust const functions and macros to allow to develop
> > KUnit tests without relying on generated C code:
> >
> >  - The `kunit_unsafe_test_suite!` Rust macro is similar to the
> >    `kunit_test_suite` C macro. It requires a NULL-terminated array of
> >    test cases (see below).
> >  - The `kunit_case` Rust function is similar to the `KUNIT_CASE` C macro.
> >    It generates as case from the name and function.
> >  - The `kunit_case_null` Rust function generates a NULL test case, which
> >    is to be used as delimiter in `kunit_test_suite!`.
> >
> > While these functions and macros can be used on their own, a future
> > patch will introduce another macro to create KUnit tests using a
> > user-space like syntax.
> >
> > Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> > Co-developed-by: Matt Gilbride <mattgilbride@google.com>
> > Signed-off-by: Matt Gilbride <mattgilbride@google.com>
> > Co-developed-by: David Gow <davidgow@google.com>
> > Signed-off-by: David Gow <davidgow@google.com>
> > ---
> >
> > Changes since v3:
> > https://lore.kernel.org/linux-kselftest/20241030045719.3085147-4-davidgow@google.com/
> > - The kunit_unsafe_test_suite!() macro now panic!s if the suite name is
> >   too long, triggering a compile error. (Thanks, Alice!)
> >
> > Changes since v2:
> > https://lore.kernel.org/linux-kselftest/20241029092422.2884505-2-davidgow@google.com/
> > - The kunit_unsafe_test_suite!() macro will truncate the name of the
> >   suite if it is too long. (Thanks Alice!)
> > - We no longer needlessly use UnsafeCell<> in
> >   kunit_unsafe_test_suite!(). (Thanks Alice!)
> >
> > Changes since v1:
> > https://lore.kernel.org/lkml/20230720-rustbind-v1-1-c80db349e3b5@google.com/
> > - Rebase on top of rust-next
> > - As a result, KUnit attributes are new set. These are hardcoded to the
> >   defaults of "normal" speed and no module name.
> > - Split the kunit_case!() macro into two const functions, kunit_case()
> >   and kunit_case_null() (for the NULL terminator).
> >
> > ---
> >  rust/kernel/kunit.rs | 112 +++++++++++++++++++++++++++++++++++++++++++
> >  rust/kernel/lib.rs   |   1 +
> >  2 files changed, 113 insertions(+)
> >
> > diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> > index 824da0e9738a..85bc1faff0d5 100644
> > --- a/rust/kernel/kunit.rs
> > +++ b/rust/kernel/kunit.rs
> > @@ -161,3 +161,115 @@ macro_rules! kunit_assert_eq {
> >          $crate::kunit_assert!($name, $file, $diff, $left == $right);
> >      }};
> >  }
> > +
> > +/// Represents an individual test case.
> > +///
> > +/// The test case should have the signature
> > +/// `unsafe extern "C" fn test_case(test: *mut crate::bindings::kunit)`.
> > +///
> > +/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases.
> > +/// Use `kunit_case_null` to generate such a delimeter.
> > +const fn kunit_case(name: &'static kernel::str::CStr, run_case: unsafe extern "C" fn(*mut kernel::bindings::kunit)) -> kernel::bindings::kunit_case {
> > +    kernel::bindings::kunit_case {
> > +        run_case: Some(run_case),
> > +        name: name.as_char_ptr(),
> > +        attr: kernel::bindings::kunit_attributes {
> > +            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> > +        },
> > +        generate_params: None,
> > +        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
> > +        module_name: core::ptr::null_mut(),
> > +        log: core::ptr::null_mut(),
> > +    }
> > +}
> > +
> > +/// Represents the NULL test case delimiter.
> > +///
> > +/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases. This
> > +/// function retuns such a delimiter.
> > +const fn kunit_case_null() -> kernel::bindings::kunit_case {
> > +    kernel::bindings::kunit_case {
> > +        run_case: None,
> > +        name: core::ptr::null_mut(),
> > +        generate_params: None,
> > +        attr: kernel::bindings::kunit_attributes {
> > +            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> > +        },
> > +        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
> > +        module_name: core::ptr::null_mut(),
> > +        log: core::ptr::null_mut(),
> > +    }
> > +}
> > +
> > +
> > +/// Registers a KUnit test suite.
> > +///
> > +/// # Safety
> > +///
> > +/// `test_cases` must be a NULL terminated array of test cases.
> > +///
> > +/// # Examples
> > +///
> > +/// ```ignore
> > +/// unsafe extern "C" fn test_fn(_test: *mut crate::bindings::kunit) {
> > +///     let actual = 1 + 1;
> > +///     let expected = 2;
> > +///     assert_eq!(actual, expected);
> > +/// }
> > +///
> > +/// static mut KUNIT_TEST_CASE: crate::bindings::kunit_case = crate::kunit_case(name, test_fn);
> > +/// static mut KUNIT_NULL_CASE: crate::bindings::kunit_case = crate::kunit_case_null();
> > +/// static mut KUNIT_TEST_CASES: &mut[crate::bindings::kunit_case] = unsafe {
> > +///     &mut[KUNIT_TEST_CASE, KUNIT_NULL_CASE]
> > +/// };
> > +/// crate::kunit_unsafe_test_suite!(suite_name, KUNIT_TEST_CASES);
> > +/// ```
> > +#[macro_export]
> > +macro_rules! kunit_unsafe_test_suite {
> > +    ($name:ident, $test_cases:ident) => {
> > +        const _: () = {
> > +            static KUNIT_TEST_SUITE_NAME: [i8; 256] = {
> > +                let name_u8 = core::stringify!($name).as_bytes();
> > +                let mut ret = [0; 256];
> > +
> > +                if name_u8.len() > 255 {
> > +                    panic!(concat!("The test suite name `", core::stringify!($name), "` exceeds the maximum length of 255 bytes."));
> > +                }
> > +
> > +                let mut i = 0;
> > +                while i < name_u8.len() {
> > +                    ret[i] = name_u8[i] as i8;
> > +                    i += 1;
> > +                }
> > +
> > +                ret
> > +            };
> > +
> > +            static mut KUNIT_TEST_SUITE: $crate::bindings::kunit_suite =
> > +                $crate::bindings::kunit_suite {
> > +                    name: KUNIT_TEST_SUITE_NAME,
> > +                    // SAFETY: User is expected to pass a correct `test_cases`, hence this macro
> > +                    // named 'unsafe'.
> > +                    test_cases: unsafe { $test_cases.as_mut_ptr() },
> > +                    suite_init: None,
> > +                    suite_exit: None,
> > +                    init: None,
> > +                    exit: None,
> > +                    attr: $crate::bindings::kunit_attributes {
> > +                        speed: $crate::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> > +                    },
> > +                    status_comment: [0; 256usize],
> > +                    debugfs: core::ptr::null_mut(),
> > +                    log: core::ptr::null_mut(),
> > +                    suite_init_err: 0,
> > +                    is_init: false,
> > +                };
> > +
> > +            #[used]
> > +            #[link_section = ".kunit_test_suites"]
> > +            static mut KUNIT_TEST_SUITE_ENTRY: *const $crate::bindings::kunit_suite =
> > +                // SAFETY: `KUNIT_TEST_SUITE` is static.
> > +                unsafe { core::ptr::addr_of_mut!(KUNIT_TEST_SUITE) };
>
> FYI, `addr_of` and `addr_of_mut` is safe now on statics since 1.82:
>
>         https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html#safely-addressing-unsafe-statics
>
> We need a `#[allow(unused_unsafe)]` here to avoid the unused unsafe
> warning.
>

I've not been able to work out how to fix this: adding
"#![allow(unused_unsafe)]" to the unsafe block here triggers another
error:
ERROR:root:error[E0658]: attributes on expressions are experimental

Is there somewhere else we can put the attribute to support this
without having to either disable the warning, or use the experimental
feature globally?

-- David

On Sat, Nov 9, 2024 at 9:18 AM David Gow <davidgow@google.com> wrote:
>
> Is there somewhere else we can put the attribute to support this
> without having to either disable the warning, or use the experimental
> feature globally?

Yeah, on the item, e.g. https://godbolt.org/z/oo8osadn4:

    const _: () = {
        static mut X: i32 = 42;

        #[allow(unused_unsafe)]
        static mut S: *const i32 = unsafe { core::ptr::addr_of_mut!(X) };
    };

Cheers,
Miguel