Re: [PATCH] xen: remove the usage of the P ar option

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Dec 31, 2020 at 03:46:50PM +0000, Andrew Cooper wrote:
> On 31/12/2020 09:20, Roger Pau Monné wrote:
> > On Wed, Dec 30, 2020 at 06:32:58PM +0000, Andrew Cooper wrote:
> >> On 30/12/2020 17:34, Roger Pau Monne wrote:
> >>> It's not part of the POSIX standard [0] and as such non GNU ar
> >>> implementations don't usually have it.
> >>>
> >>> It's not relevant for the use case here anyway, as the archive file is
> >>> recreated every time due to the rm invocation before the ar call. No
> >>> file name matching should happen so matching using the full path name
> >>> or a relative one should yield the same result.
> >>>
> >>> This fixes the build on FreeBSD.
> >>>
> >>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> >> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although...
> >>
> >> We really need some kind of BSD build in CI.  This kind of breakage
> >> shouldn't get into master to begin with.
> > Fully agree. I'm not that familiar with gitlab CI, but since we have
> > our own runners there, could we also launch VMs instead of just using
> > containers?
> >
> > It might be easier to integrate with osstest in the future, since
> > FreeBSD has now switched to git.
> >
> >>> [0] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/ar.html
> >>> ---
> >>> I'm unsure whether the r and s options are also needed, since they
> >>> seem to only be relevant when updating a library, and Xen build system
> >>> always removes the old library prior to any ar call.
> >> ... I think r should be dropped, because we're not replacing any files. 
> >> However, I expect the index file is still relevant, because without it,
> >> you've got to perform an O(n) search through the archive to find a file.
> > Right, the description of 's' between opengroup and the Linux man page
> > seems to be slightly different. From the opengroup description it seems
> > like s should be used to force the generation of a symbol table when
> > no changes are made to the archive, but otherwise ar should already
> > generate such symbol table.
> 
> Ok - are you happy for me to commit with dropping the r and s?

So after testing this, I think we need at least the r option, as we
want to add new files to the archive (regardless of whether it exists
or not). That seems to be mandatory on FreeBSD, as calling 'ar c' is
not valid.

I think s can be dropped, as ar will generate the symbol table by
default unless S is specified. s should just be used to force the
generation of a symbol table when not adding files and the archive has
been stripped AFAICT.

If so would you mind adding:

"While there also drop the s option, as ar will already generate a
symbol table by default when creating the archive."

To the commit message if you end up dropping s?

Thanks, Roger.