Re: [PATCH v2 1/2] rust: pin-init: internal: init: remove `#[disable_initialized_field_access]`

[Benno Lossin]

On Tue Mar 3, 2026 at 12:31 PM CET, Alice Ryhl wrote:
> On Mon, Mar 02, 2026 at 03:04:14PM +0100, Benno Lossin wrote:
>> Gary noticed [1] that the initializer macros as well as the `[Pin]Init`
>> traits cannot support unaligned fields, since they use operations that
>> require aligned pointers. This means that any code using structs with
>> unaligned fields in pin-init is unsound.
>> 
>> By default, the `init!` macro generates references to initialized
>> fields, which makes the compiler check that those fields are aligned.
>> However, we added the `#[disable_initialized_field_access]` attribute to
>> avoid this behavior in ceca298c53f9 ("rust: pin-init: internal: init:
>
> checkpatch here: missing 'commit' before ceca298c53f9

I'll let Miguel adjust that when picking the patch :)

>> add escape hatch for referencing initialized fields"). Thus remove the
>> `#[disable_initialized_field_access]` attribute from `init!`, which is
>> the only safe way to create an initializer handling unaligned fields.
>> 
>> If support for in-place initializing structs with unaligned fields is
>> required in the future, we could figure out a solution. This is tracked
>> in [2].
>> 
>> Reported-by: Gary Guo <gary@xxxxxxxxxxx>
>> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
>
> Should probably be Closes: rather than Link:.

I figured that we can't really "close" a Zulip topic (we can mark it as
completed, but that topic was originally about the field accessors, so
not sure if this makes much sense.

Cheers,
Benno