On Mon Mar 2, 2026 at 5:20 PM GMT, Tamir Duberstein wrote:
> Now that all literals are C-Strings, rename and update the documentation
> of this macro to clarify its intended purpose.
>
> Link: https://github.com/Rust-for-Linux/linux/issues/1075
> Acked-by: Greg Kroah-Hartman <[email protected]>
> Reviewed-by: Alice Ryhl <[email protected]>
> Signed-off-by: Tamir Duberstein <[email protected]>
Do we really need to perform the rename? I think updating the documentation
should be good enough?
If the only concern is misuse of the macro then perhaps I can just add a
lint for this in klint.
> ---
> This patch completes the work of replacing our custom `CStr` with
> upstream's.
> ---
> rust/kernel/bug.rs | 2 +-
> rust/kernel/configfs.rs | 2 +-
> rust/kernel/drm/ioctl.rs | 2 +-
> rust/kernel/kunit.rs | 3 ++-
> rust/kernel/str.rs | 19 ++++++++++++++-----
> rust/kernel/sync.rs | 4 ++--
> rust/kernel/sync/lock/global.rs | 3 ++-
> rust/kernel/workqueue.rs | 6 +++---
> 8 files changed, 26 insertions(+), 15 deletions(-)
>
> diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
> index ed943960f851..f7cb673b1766 100644
> --- a/rust/kernel/bug.rs
> +++ b/rust/kernel/bug.rs
> @@ -80,7 +80,7 @@ macro_rules! warn_flags {
> // with a valid null-terminated string.
> unsafe {
> $crate::bindings::warn_slowpath_fmt(
> - $crate::c_str!(::core::file!()).as_char_ptr(),
> + $crate::str_to_cstr!(::core::file!()).as_char_ptr(),
> line!() as $crate::ffi::c_int,
> $flags as $crate::ffi::c_uint,
> ::core::ptr::null(),
> diff --git a/rust/kernel/configfs.rs b/rust/kernel/configfs.rs
> index 2339c6467325..930f17bb2041 100644
> --- a/rust/kernel/configfs.rs
> +++ b/rust/kernel/configfs.rs
> @@ -1000,7 +1000,7 @@ macro_rules! configfs_attrs {
> $crate::configfs::Attribute<$attr, $data, $data> =
> unsafe {
> $crate::configfs::Attribute::new(
> -
> $crate::c_str!(::core::stringify!($name)),
> +
> $crate::str_to_cstr!(::core::stringify!($name)),
> )
> };
> )*
> diff --git a/rust/kernel/drm/ioctl.rs b/rust/kernel/drm/ioctl.rs
> index cf328101dde4..6a87f489dc88 100644
> --- a/rust/kernel/drm/ioctl.rs
> +++ b/rust/kernel/drm/ioctl.rs
> @@ -157,7 +157,7 @@ macro_rules! declare_drm_ioctls {
> },
> flags: $flags,
> name: $crate::str::as_char_ptr_in_const_context(
> - $crate::c_str!(::core::stringify!($cmd)),
> + $crate::str_to_cstr!(::core::stringify!($cmd)),
> ),
> }
> ),*];
> diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> index f93f24a60bdd..5802a3507ecc 100644
> --- a/rust/kernel/kunit.rs
> +++ b/rust/kernel/kunit.rs
> @@ -59,7 +59,8 @@ macro_rules! kunit_assert {
>
> static FILE: &'static $crate::str::CStr = $file;
> static LINE: i32 = ::core::line!() as i32 - $diff;
> - static CONDITION: &'static $crate::str::CStr =
> $crate::c_str!(stringify!($condition));
> + static CONDITION: &'static $crate::str::CStr =
> + $crate::str_to_cstr!(stringify!($condition));
>
> // SAFETY: FFI call without safety requirements.
> let kunit_test = unsafe {
> $crate::bindings::kunit_get_current_test() };
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index fa87779d2253..8bb40de007d4 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -376,19 +376,28 @@ fn as_ref(&self) -> &BStr {
> }
> }
>
> -/// Creates a new [`CStr`] from a string literal.
> +/// Creates a new [`CStr`] at compile time.
> ///
> -/// The string literal should not contain any `NUL` bytes.
> +/// Rust supports C string literals since Rust 1.77, and they should be used
> instead of this macro
> +/// where possible. This macro exists to allow static *non-literal* C
> strings to be created at
> +/// compile time. This is most often used in other macros.
> +///
> +/// # Panics
> +///
> +/// This macro panics if the operand contains an interior `NUL` byte.
> ///
> /// # Examples
> ///
> /// ```
> -/// # use kernel::c_str;
> +/// # use kernel::str_to_cstr;
> /// # use kernel::str::CStr;
> -/// const MY_CSTR: &CStr = c_str!("My awesome CStr!");
> +/// const MY_CSTR: &CStr = str_to_cstr!(concat!(file!(), ":", line!(), ": My
> CStr!"));
Perhaps keep a copy of the old example and add a comment saying this is allowed
but c"literal" should be preferred.
Best,
Gary
> /// ```
> #[macro_export]
> -macro_rules! c_str {
> +macro_rules! str_to_cstr {
> + // NB: we could write `($str:lit) => compile_error!("use a C string
> literal instead");` here but
> + // that would trigger when the literal is at the top of several macro
> expansions. That would be
> + // too limiting to macro authors, so we rely on the name as a hint
> instead.
> ($str:expr) => {{
> const S: &str = concat!($str, "\0");
> const C: &$crate::str::CStr = match
> $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index 993dbf2caa0e..ecf02a67ec35 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -154,9 +154,9 @@ macro_rules! static_lock_class {
> #[macro_export]
> macro_rules! optional_name {
> () => {
> - $crate::c_str!(::core::concat!(::core::file!(), ":",
> ::core::line!()))
> + $crate::str_to_cstr!(::core::concat!(::core::file!(), ":",
> ::core::line!()))
> };
> ($name:literal) => {
> - $crate::c_str!($name)
> + $crate::str_to_cstr!($name)
> };
> }
> diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
> index aecbdc34738f..81f46229be7d 100644
> --- a/rust/kernel/sync/lock/global.rs
> +++ b/rust/kernel/sync/lock/global.rs
> @@ -272,7 +272,8 @@ macro_rules! global_lock {
> $pub enum $name {}
>
> impl $crate::sync::lock::GlobalLockBackend for $name {
> - const NAME: &'static $crate::str::CStr =
> $crate::c_str!(::core::stringify!($name));
> + const NAME: &'static $crate::str::CStr =
> + $crate::str_to_cstr!(::core::stringify!($name));
> type Item = $valuety;
> type Backend = $crate::global_lock_inner!(backend $kind);
>
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index 706e833e9702..7616d71df68e 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -212,7 +212,7 @@ macro_rules! new_delayed_work {
> $crate::workqueue::DelayedWork::new(
> $crate::optional_name!(),
> $crate::static_lock_class!(),
> - $crate::c_str!(::core::concat!(
> + $crate::str_to_cstr!(::core::concat!(
> ::core::file!(),
> ":",
> ::core::line!(),
> @@ -223,9 +223,9 @@ macro_rules! new_delayed_work {
> };
> ($name:literal) => {
> $crate::workqueue::DelayedWork::new(
> - $crate::c_str!($name),
> + $crate::str_to_cstr!($name),
> $crate::static_lock_class!(),
> - $crate::c_str!(::core::concat!($name, "_timer")),
> + $crate::str_to_cstr!(::core::concat!($name, "_timer")),
> $crate::static_lock_class!(),
> )
> };
>
> ---
> base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
> change-id: 20260302-cstr-rename-macro-64201be6c969
>
> Best regards,
> --
> Tamir Duberstein <[email protected]>
