Re: [PATCH] rust: introduce alternative implementation of offset_of!

[Junjie Mao <junjie.mao@hotmail.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> Il lun 21 ott 2024, 09:24 Junjie Mao <junjie.mao@hotmail.com> ha scritto:
>
>  > Thanks.  I still prefer to keep the procedural macro code minimal, and have the
>  > code generation in a separate macro, but this is a nice start!
>  >
>
>  I'm not sure if I get your point right.
>
>  My understanding is that preferring minimizing proc macros is because
>  they generate a big, arbitrary block of code that is hard to read and
>  debug directly (which requires cargo expand the whole crate). That is
>  thus more error-prone and makes maintenance harder.
>
>  As for having "the code generation in a separate macro", are you
>  referring to `macro_rules!`?
>
> Yes, keeping the generation of the impl block in with_offsets!. Then you can get the best of both worlds in my opinion, for example the #[repr(C)] check is more robust in the procedural macro.

Got it. Will try that approach in v2.

>
>  Sure. Will use quote_spanned! here and make reported errors being a
>  tuple of error msg and span to use.
>
> If it's okay for you let's first get the fixes in, and then I can repost the MSRV series and include your procedural macro and unit tests.

The v2 fixes look good to me overall. Thanks!

--
Best Regards
Junjie Mao