Re: [PATCH v7 23/26] rust: str: test: replace `alloc::format`

Gary Guo
2024-09-28T19:37:42Z

On Thu, 12 Sep 2024 00:52:59 +0200
Danilo Krummrich <dakr@kernel.org> 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`.
>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
> 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 209ad1bb1a49..726329530338 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()
> + }
> + }
> +
> + macro_rules! format {
> + ($($f:tt)*) => ({
> + &*String::from_fmt(kernel::fmt!($($f)*))
> + })
> + }
>
> const ALL_ASCII_CHARS: &'static str =
> "\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\x09\\x0a\\x0b\\x0c\\x0d\\x0e\\x0f\