Re: [XEN PATCH] build: Fix x86 build without EFI

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, Aug 16, 2022 at 03:02:10PM +0200, Jan Beulich wrote:
> On 16.08.2022 12:30, Anthony PERARD wrote:
> > We can't have a source file with the same name that exist in both the
> > common code and in the arch specific code for efi/. This can lead to
> > comfusion in make and it can pick up the wrong source file. This issue
> > lead to a failure to build a pv-shim for x86 out-of-tree, as this is
> > one example of an x86 build using the efi/stub.c.
> > 
> > The issue is that in out-of-tree, make might find x86/efi/stub.c via
> > VPATH, but as the target needs to be rebuilt due to FORCE, make
> > actually avoid changing the source tree and rebuilt the target with
> > VPATH ignored, so $@ lead to the build tree where "stub.c" dosen't
> > exist yet so a link is made to "common/stub.c".
> > 
> > Rework the new common/stub.c file to have a different name than the
> > already existing one. And build both *stub.c as two different objects.
> > This mean we have to move some efi_compat_* aliases which are probably
> > useless for Arm.
> 
> These useless aliases want avoiding there imo. Already when the original
> series was discussed, I requested to avoid introduction of a file named
> common-stub.c or alike.

Yeah, I've notice that. This is why the build is broken under
specific condition.

> If names need to be different, can't we follow
> boot.c's model and introduce a per-arch efi/stub.h which stub.c would
> include at a suitable position (and which right now would be empty for
> Arm)?

That seems to be possible. But how is it better than having two
different source file? The only thing is to avoid exporting the
efi_compat_* symbol aliases. The downside is we would have another weird
looking not really header which is actually just part of a source file.
At least, "stub.c" and "stub.h" would be two different names, we just
change the extension rather than the basename.

Cheers,

-- 
Anthony PERARD