Re: [PATCH] rust: query the compiler for dylib path

[Tamir Duberstein <tamird@gmail.com>]

On Mon, Oct 14, 2024 at 3:09 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Mon, Oct 14, 2024 at 8:46 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > rustc ignores --emit=link=rust/libmacro.so
> > and produces rust/libmacro.dylib.
> >
> > Is this a bug in rustc?

This was my bad - I set this thread down the wrong path. In fact the
current build produces libmacros.so, but I haven't been able to convince
rustc to consume it. Changing `--extern macros` to `--extern
macros=$(objtree)/$(obj)/libmacros.so` produces 'error[E0463]: can't
find crate for `macros`'.

With a toy example, trying to link a proc-macro crate .so produces a
more informative message than the kernel build does:
```
 rustc main.rs --extern macros=./libmacros.so
error: extern location for macros is of an unknown type: ./libmacros.so
 --> main.rs:4:1
  |
4 | extern crate macros;
  | ^^^^^^^^^^^^^^^^^^^^

error: file name should be lib*.rlib or lib*.dylib
 --> main.rs:4:1
  |
4 | extern crate macros;
  | ^^^^^^^^^^^^^^^^^^^^
```

I've opened https://github.com/rust-lang/rust/issues/131720, let's see
what the experts think.