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

Danilo Krummrich
2024-08-12T13:08:01Z

On 8/8/24 9:22 AM, Benno Lossin wrote:
> 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.

Right, but I thought it's a bit more extensible and cleaner than...

>
>> +
>> + 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()

...doing it inline.

I'm fine either way, but unless you really want me to change it, I'd
rather keep it as it is.

>
> ---
> 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
>>
>