Re: [PATCH v2 1/2] rust: Update PCI binding safety comments and add inline compiler hint

[Benno Lossin]

On Tue Jul 22, 2025 at 1:35 PM CEST, Alice Ryhl wrote:
> On Tue, Jul 22, 2025 at 12:57 PM Benno Lossin <lossin@xxxxxxxxxx> wrote:
>>
>> On Tue Jul 22, 2025 at 11:51 AM CEST, Danilo Krummrich wrote:
>> > I think they're good, but we're pretty late in the cycle now. That should be
>> > fine though, we can probably take them through the nova tree, or in the worst
>> > case share a tag, if needed.
>> >
>> > Given that, it would probably be good to add the Guarantee section on as_raw(),
>> > as proposed by Benno, right away.
>> >
>> > @Benno: Any proposal on what this section should say?
>>
>> At a minimum I'd say "The returned pointer is valid.", but that doesn't
>> really say for what it's valid... AFAIK you're mostly using this pointer
>> to pass it to the C side, in that case, how about:
>>
>>     /// # Guarantees
>>     ///
>>     /// The returned pointer is valid for reads and writes from the C side for as long as `self` exists.
>>
>> Maybe we need to change it a bit more, but let's just start with this.
>>
>> (If you're also using the pointer from Rust, then we need to make
>> changes)
>
> Honestly I think this is a bit over the top. I wouldn't bother adding
> a section like that to every single as_raw() method out there.

Hmm. And then just assume that these kinds of functions return valid
pointers? I get that this is annoying to put on every function...

Another option would be to have a `Ptr<'a, T>` type that is a valid
pointer, but doesn't allow writing/reading safely (you need to justify
why it's not a data race). And for FFI there could be an `as_ptr`
function.

---
Cheers,
Benno