Re: XenSummit: Empty per-arch files

[Juergen Gross <jgross@xxxxxxxx>]

On 28.06.23 15:46, Andrew Cooper wrote:
> On 28/06/2023 2:26 pm, Juergen Gross wrote:
> > On 28.06.23 13:32, Andrew Cooper wrote:
> > > Hello,
> > >
> > > This wasn't a formal discussion point at XenSummit, but Oleksii pointed
> > > out that it was still a problem, hence this thread.
> > >
> > > As we take on more architectures, it becomes more and more important for
> > > things to be handled in a mostly-common way.  With that comes quite a
> > > lot of <xen/foo.h> including <asm/foo.h>, and the arch one being a stub
> > > in simple cases.
> > >
> > > It would be nice to get rid of the stub files; they're irritating to
> > > deal with, both when refactoring and simply for the file bloat they
> > > create.
> > >
> > > There are two options which come to mind.
> > >
> > > 1) Use __has_include().  This would be ideal, but would require us
> > > bumping the minimum GCC version to 4.9.2 as a prerequisite.  I'm not
> > > aware of any way to emulate the necessary behaviour on older toolchains.
> > >
> > > 2) Have a stub "architecture" which is always last on the include path.
> > > This would reduce the number of stub files from one set per arch, to
> > > only one set.
> > >
> > > Anything else that I've missed?
> > What about a make rule creating an empty include file if it is missing?
> Wouldn't that cause a typo'd header file name to spring into existence ?
>
> And it would cause a build to leave the working tree dirty.
Depends how it is done.

There could be a file containing the allowed header names to be generated.

And the files wouldn't need to be generated in arch/<arch>/include/asm, but
could be generated in e.g. include/generated/asm which would be used after
the arch include path.

This would basically be the central stub variant you were mentioning, but
building it dynamically.


Juergen

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