Re: [PATCH 2/2] rust: alloc: add `Vec::dec_len`

Benno Lossin
2025-03-17T17:25:05Z

On Mon Mar 17, 2025 at 4:37 PM CET, Tamir Duberstein wrote:
> On Mon, Mar 17, 2025 at 10:39 AM Benno Lossin <benno.lossin@proton.me> wrote:
>> On Mon Mar 17, 2025 at 12:34 PM CET, Tamir Duberstein wrote:
>> > On Mon, Mar 17, 2025 at 6:04 AM Benno Lossin <benno.lossin@proton.me> wrote:
>> >> On Sun Mar 16, 2025 at 11:32 PM CET, Tamir Duberstein wrote:
>> >> > + ///
>> >> > + /// # Safety
>> >> > + ///
>> >> > + /// - `count` must be less than or equal to `self.len`.
>> >>
>> >> I also think that we should use saturating_sub instead and then not have
>> >> to worry about this. (It should still be documented in the function
>> >> though). That way this can also be a safe function.
>> >
>> > This doesn't seem better to me. I'd prefer to have more rather than
>> > fewer guardrails on such low-level operations.
>>
>> Your second sentence seems like an argument for making it safe? I think
>> it's a lot better as a safe function.
>
> The guardrail I was referring to is the requirement that the caller
> write a safety comment.

But saturating_sub is a better guardrail?

---
Cheers,
Benno