"Benno Lossin" <los...@kernel.org> writes:
> On Thu Jun 19, 2025 at 2:20 PM CEST, Andreas Hindborg wrote:
>> "Benno Lossin" <los...@kernel.org> writes:
>>> On Thu Jun 12, 2025 at 3:40 PM CEST, Andreas Hindborg wrote:
[...]
>>>> + crate::error::from_result(|| {
>>>> + let new_value = T::try_from_param_arg(arg)?;
>>>> +
>>>> + // SAFETY: By function safety requirements `param` is be valid
>>>> for reads.
>>>> + let old_value = unsafe { (*param).__bindgen_anon_1.arg as *mut T
>>>> };
>>>> +
>>>> + // SAFETY: By function safety requirements, the target of
>>>> `old_value` is valid for writes
>>>> + // and is initialized.
>>>> + unsafe { *old_value = new_value };
>>>
>>> So if we keep the `ModuleParam: Copy` bound from above, then we don't
>>> need to drop the type here (as `Copy` implies `!Drop`). So we could also
>>> remove the requirement for initialized memory and use `ptr::write` here
>>> instead. Thoughts?
>>
>> Yes, that is the rationale for the `Copy` bound. What would be the
>> benefit of using `ptr::write`? They should be equivalent for `Copy`
>> types, right.
>
> They should be equivalent, but if we drop the requirement that the value
> is initialized to begin with, then removing `Copy` will result in UB
> here.
>
>> I was using `ptr::replace`, but Alice suggested the pace expression
>> assignment instead, since I was not using the old value.
>
> That makes sense, but if we also remove the initialized requirement,
> then I would prefer `ptr::write`.
OK, we can do that.
Best regards,
Andreas Hindborg
