On Sat May 24, 2025 at 10:33 PM CEST, Tamir Duberstein wrote:
> -/// Creates a new [`CStr`] from a string literal.
> +/// Creates a static C string wrapper 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::c_str_avoid_literals;
> /// # use kernel::str::CStr;
> -/// const MY_CSTR: &CStr = c_str!("My awesome CStr!");
> +/// const MY_CSTR: &CStr = c_str_avoid_literals!(concat!(file!(), ":",
> line!(), ": My CStr!"));
> /// ```
> #[macro_export]
> -macro_rules! c_str {
> +macro_rules! c_str_avoid_literals {
I don't like this name, how about `concat_to_c_str` or
`concat_with_nul`?
This macro also is useful from macros that have a normal string literal,
but can't turn it into a `c""` one.
> + // 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
> $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
> - Ok(v) => v,
> - Err(_) => panic!("string contains interior NUL"),
> - };
> + const S: &'static str = concat!($str, "\0");
> + const C: &'static $crate::str::CStr =
> + match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
Why is this still our CStr?
> + Ok(v) => v,
> + Err(err) => {
> + let _: core::ffi::FromBytesWithNulError = err;
Is this really necessary?
---
Cheers,
Benno
> + panic!("string contains interior NUL")
> + }
> + };
> C
> }};
> }
