Re: [PATCH] selftests: default to host arch for LLVM builds

[Shuah Khan]

On 4/28/24 06:08, Valentin Obst wrote:
> > > Align the behavior for gcc and clang builds by interpreting unset
> > > `ARCH` and `CROSS_COMPILE` variables in `LLVM` builds as a sign that the
> > > user wants to build for the host architecture.
> > >
> > > This patch preserves the properties that setting the `ARCH` variable to an
> > > unknown value will trigger an error that complains about insufficient
> > > information, and that a set `CROSS_COMPILE` variable will override the
> > > target triple that is determined based on presence/absence of `ARCH`.
> > >
> > > When compiling with clang, i.e., `LLVM` is set, an unset `ARCH` variable in
> > > combination with an unset `CROSS_COMPILE` variable, i.e., compiling for
> > > the host architecture, leads to compilation failures since `lib.mk` can
> > > not determine the clang target triple. In this case, the following error
> > > message is displayed for each subsystem that does not set `ARCH` in its
> > > own Makefile before including `lib.mk` (lines wrapped at 75 chrs):
> > >
> > >     make[1]: Entering directory '/mnt/build/linux/tools/testing/selftests/
> > >      sysctl'
> > >     ../lib.mk:33: *** Specify CROSS_COMPILE or add '--target=' option to
> > >      lib.mk.  Stop.
> > >     make[1]: Leaving directory '/mnt/build/linux/tools/testing/selftests/
> > >      sysctl'
> >
> > Thanks for fixing this.
> >
> > And yes, the selftests "normal" (non-cross-compile) build is *broken*
> > right now, for clang. I didn't realize from the patch title that this is
> > actually a significant fix. Maybe we should change the subject line (patch
> > title) to something like:
> >
> >      [PATCH] selftests: fix the clang build: default to host arch for LLVM builds
>
> Yes, I agree that the title should contain the word 'fix' somewhere. For
> me its okay if maintainers reword the title when applying the patch,
> alternatively I can send a v2. (Is it still a v2 if I change the title, or
> rather a new patch?).
>
> Any thoughts on whether this also needs a 'Cc stable'? Its not quite
> clear to me if this fix meets the requirements. As above, no objections if
> maintainers should decide to add it.
>
> > ?
> >
> > Just a thought. The "Fixes:" tag covers it already, I realize.
> >
> > Anyway, this looks correct, and fixes that aspect of the build for me, so
> > either way, please feel free to add:
> >
> > Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

Thanks for the patch. Applied to linux-kselftest next for Linux 6.10-rc1

thanks,
-- Shuah