On Thu, Dec 04, 2025 at 01:39:06PM +0100, Peter Zijlstra wrote: > On Thu, Dec 04, 2025 at 12:57:31PM +0100, 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. > > > > > ... if you build rustc against libclang they are necessarily from the > > > same LLVM build. > > > > So currently there are 3 "LLVMs" that get involved: > > > > - The one Clang uses (in LLVM=1 builds). > > Well, being on Debian, I'm more likely to be using LLVM=-22 (or whatever > actual version is required, 22 just being the latest shipped by Debian > at this point in time). > > > - The one `rustc` uses (the LLVM backend). > > - The one `bindgen` uses (via libclang). > > These are not necessarily the same? That is, is not bindgen part of the > rustc project and so would be built against the same LLVM?
Rustc and bindgen are both part of the Rust project, but they're two different repos: https://github.com/rust-lang/rust https://github.com/rust-lang/rust-bindgen Generally you need to ensure that bindgen matches clang. This ensures that bindgen and clang agree on the interpretation of C headers. > > If that is all done within `rustc` (so no `bindgen`), then there may > > still be `rustc` vs. Clang mismatches, which are harder to resolve in > > the Rust side at least (it is easier to pick another Clang version to > > match). > > > > For those using builds from distros, that shouldn't be a problem. > > Others using external `rustc` builds, e.g. from `rustup` (e.g. for > > testing different Rust versions) it would be harder. > > Make rust part of LLVM and get them all built and distributed > together... such that LLVM=-23 will get me a coherent set of tools. > > /me runs like crazeh ;-) Maybe clang itself should have an option to emit Rust headers, taking over the role of bindgen? /me runs like crazeh ;-) Alice
