Re: linux-next: build failure after merge of the rust tree

[Alice Ryhl]

On Fri, Jan 10, 2025 at 10:41 AM Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:
>
> On Fri, Jan 10, 2025 at 10:34 AM Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Fri, Jan 10, 2025 at 10:28:46AM +0100, Alice Ryhl wrote:
> > > On Fri, Jan 10, 2025 at 6:28 AM Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > After merging the rust tree, today's linux-next build (x86_64
> > > > allmodconfig) failed like this:
> > > >
> > > > error[E0423]: expected function, found macro `kernel::build_error`
> > > >    --> rust/kernel/miscdevice.rs:159:9
> > > >     |
> > > > 159 |         kernel::build_error(VTABLE_DEFAULT_ERROR)
> > > >     |         ^^^^^^^^^^^^^^^^^^^ not a function
> > > >     |
> > > > help: use `!` to invoke the macro
> > > >     |
> > > > 159 |         kernel::build_error!(VTABLE_DEFAULT_ERROR)
> > > >     |                            +
> > > > help: consider importing one of these functions instead
> > > >     |
> > > > 11  + use crate::build_assert::build_error;
> > > >     |
> > > > 11  + use build_error::build_error;
> > > >     |
> > > > help: if you import `build_error`, refer to it directly
> > > >     |
> > > > 159 -         kernel::build_error(VTABLE_DEFAULT_ERROR)
> > > > 159 +         build_error(VTABLE_DEFAULT_ERROR)
> > > >     |
> > > >
> > > > error: aborting due to 1 previous error
> > > >
> > > > For more information about this error, try `rustc --explain E0423`.
> > > >
> > > > Caused by commit
> > > >
> > > >   614724e780f5 ("rust: kernel: move `build_error` hidden function to prevent mistakes")
> > > >
> > > > interacting with commit
> > > >
> > > >   5bcc8bfe841b ("rust: miscdevice: add fops->show_fdinfo() hook")
> > > >
> > > > from the driver-core tree.
> > > >
> > > > I have added the following merge resolution patch.
> > > >
> > > > From: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > > > Date: Fri, 10 Jan 2025 16:02:19 +1100
> > > > Subject: [PATCH] fix up for "rust: kernel: move `build_error` hidden function
> > > >  to prevent mistakes"
> > > >
> > > > interacting with commit
> > > >
> > > >   5bcc8bfe841b ("rust: miscdevice: add fops->show_fdinfo() hook")
> > > >
> > > > from the driver-core tree.
> > > >
> > > > Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > > > ---
> > > >  rust/kernel/miscdevice.rs | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
> > > > index 9685e50b100d..3ba018651bc0 100644
> > > > --- a/rust/kernel/miscdevice.rs
> > > > +++ b/rust/kernel/miscdevice.rs
> > > > @@ -156,7 +156,7 @@ fn show_fdinfo(
> > > >          _m: &SeqFile,
> > > >          _file: &File,
> > > >      ) {
> > > > -        kernel::build_error(VTABLE_DEFAULT_ERROR)
> > > > +        build_error!(VTABLE_DEFAULT_ERROR)
> > > >      }
> > > >  }
> > >
> > > Thank you, this fix is correct. Greg, can you pick this up directly,
> > > or do you want a real patch?
> >
> > Can I take this as a real patch for my tree?  Or is this only an issue
> > due to the trees being merged?
>
> You can take it as a real patch. That will make your tree compile both
> with and without rust-next merged.
>
> Though I guess it would be nice to update all three instances of
> build_error! if we make a real patch. (The other two instances are
> updated in rust-next, so they don't cause the failure.)

Actually, it looks like I am mistaken. This patch doesn't build without
https://lore.kernel.org/all/20241123222849.350287-3-ojeda@xxxxxxxxxx/

I'll send a real patch.

Alice