On Tue Jul 22, 2025 at 2:49 PM CEST, Danilo Krummrich wrote: > On Tue Jul 22, 2025 at 2:08 PM CEST, Benno Lossin wrote: >> 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. > > I don't understand where's the difference between the two. For FFI calls we'd > also have to justify it's not a data race, no? Yes, but there you need a raw pointer. > The only guarantee we take as granted from as_raw() is that it returns a raw > pointer to the wrapped FFI type in Self, i.e. it points to valid memory. Any > additional guarantees may come from the context where the pointer is used and > which specific fields it is used to access. Sure you need additional guarantees from the context, but you also need the fact that the pointer coming from `as_raw` isn't just a random pointer, but that it is derived from the reference... I don't have any good plan forward for this, so maybe we should revisit this in the future... --- Cheers, Benno
