On 12/4/25 12:57 PM, Miguel Ojeda wrote:
On Thu, Dec 4, 2025 at 12:11 PM Peter Zijlstra <[email protected]> wrote:
Right. Earlier I also proposed using libclang to parse the C header and
inject that. This might be a little simpler, in that..
Yeah, that would be closer to the `bindgen` route in that `libclang`
gets already involved.
Yeah, so... there are existing tools (c2rust [0] being the actively
maintained one IIUC) that in theory could do something like that
(translate the bodies of the functions from C to Rust so that rustc
could consume them directly rather than via LLVM LTO).
I think the intended use case is more "translate a whole C project into
rust", but it could be interesting to test how well / poorly it performs
with the kernel helpers / with a single header translated to Rust.
I personally haven't tried it because for work I need to deal with C++,
which means that automatic translation to Rust is a lot harder /
probably impossible in general. So for Firefox we end up relying on
bindgen + cross-language LTO for this kind of thing, and it works well
for us.
If I'm understanding correctly, it seems the kernel needs this extra bit
of help (__always_inline) to push LLVM to inline C functions into rust,
which is a bit unfortunate... But this approach seems sensible to me,
for now at least.
FWIW Bindgen recently gained an option to generate inline functions [1],
which could help avoid at least the bindgen ifdef in the patch series?
Anyways, it might be interesting to give c2rust a go on the kernel
helpers if nobody has done so, and see how well / poorly it works in
practice? Of course probably introducing a new dependency would be kind
of a pain, but could be a good data point for pushing into adding
something like it built into rustc...
Thanks,
-- Emilio
[0]: https://github.com/immunant/c2rust
[1]:
https://docs.rs/bindgen/latest/bindgen/struct.Builder.html#method.generate_inline_functions
