Re: [PATCH v3] Kbuild: fix issues with rustc-option

[Alice Ryhl]

On Wed, Oct 9, 2024 at 2:53 PM Miguel Ojeda
<miguel.ojeda.sandonis@xxxxxxxxx> wrote:
>
> On Wed, Oct 9, 2024 at 1:42 PM Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:
> >
> > Note that RUSTC_BOOTSTRAP is also defined in the top-level Makefile, but
> > its value is unfortunately *not* inherited from the environment. That
>
> I would perhaps say ", but Make-exported variables are not inherited"
> or similar to be a bit more precise (because the external environment,
> as in the `make` environment, is exported unlike those variables).
>
> > not look for the standard library. It's not possible to instead supply a
> > standard library to rustc, as we need `rustc-option` before the Rust
> > standard library is compiled.
>
> The error message mentions `std`, so to clarify I would perhaps add
> ".... standard library (i.e. `core`)" or similar, i.e. one could think
> `no_std` is enough otherwise (which would be better if we could, since
> it is stable unlike `no_core`, but we don't want it here either).
>
> > The -o and --out-dir parameters are altered to fix this warning:
> >
> >         warning: ignoring --out-dir flag due to -o flag
> >
> > The --sysroot flag is provided as we would otherwise require it to be
> > present in KBUILD_RUSTFLAGS. The --emit=obj flag is used to write the
> > resulting rlib to /dev/null instead of writing it to a file in
> > $(TMPOUT).
>
> "the resulting object file" (i.e. the rlib is not written even if we
> wrote to a file).
>
> > I verified that the Kconfig version of rustc-option doesn't have the
> > same issues.
>
> Thanks for checking this. We may want to make it closer to what we do
> her, but that can be done later.
>
> Cheers,
> Miguel

That all sounds good to me. Feel free to make the suggested rewordings
when you apply this. Otherwise I can send a v4 if you prefer.

Alice