Re: [PATCH v4 26/28] rust: str: test: replace `alloc::format`

Benno Lossin
2024-08-08T07:23:44Z

On 05.08.24 17:19, Danilo Krummrich wrote:
> The current implementation of tests in str.rs use `format!` to format
> strings for comparison, which, internally, creates a new `String`.
>
> In order to prepare for getting rid of Rust's alloc crate, we have to
> cut this dependency. Instead, implement `format!` for `CString`.
>
> Note that for userspace tests, `Kmalloc`, which is backing `CString`'s
> memory, is just a type alias to `Cmalloc`.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
> rust/kernel/str.rs | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 0b6ffbade521..8f234224cbf5 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -523,7 +523,28 @@ macro_rules! c_str {
> #[cfg(test)]
> mod tests {
> use super::*;
> - use alloc::format;
> +
> + struct String(CString);
> +
> + impl String {
> + fn from_fmt(args: fmt::Arguments<'_>) -> Self {
> + String(CString::try_from_fmt(args).unwrap())
> + }
> + }
> +
> + impl Deref for String {
> + type Target = str;
> +
> + fn deref(&self) -> &str {
> + self.0.to_str().unwrap()
> + }
> + }

Don't actually think we need this newtype.

> +
> + macro_rules! format {
> + ($($f:tt)*) => ({
> + &*String::from_fmt(kernel::fmt!($($f)*))

We could just do this:

CString::try_from_fmt(kernel::fmt!($(f)*)).unwrap().to_str().unwrap()

---
Cheers,
Benno

> + })
> + }
>
> const ALL_ASCII_CHARS: &'static str =
> "\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\x09\\x0a\\x0b\\x0c\\x0d\\x0e\\x0f\
> --
> 2.45.2
>