Re: [Qemu-devel] [PATCH v2] configure: use pkg-config for obtaining xen version

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Juergen Gross [mailto:jgross@suse.com]
> Sent: 27 March 2017 10:15
> To: Paul Durrant <Paul.Durrant@citrix.com>; qemu-devel@nongnu.org; xen-
> devel@lists.xenproject.org
> Cc: Anthony Perard <anthony.perard@citrix.com>; kraxel@redhat.com;
> sstabellini@kernel.org
> Subject: Re: [PATCH v2] configure: use pkg-config for obtaining xen version
> 
> On 27/03/17 11:07, Paul Durrant wrote:
> >> -----Original Message-----
> >> From: Juergen Gross [mailto:jgross@suse.com]
> >> Sent: 27 March 2017 08:43
> >> To: qemu-devel@nongnu.org; xen-devel@lists.xenproject.org
> >> Cc: Anthony Perard <anthony.perard@citrix.com>; kraxel@redhat.com;
> >> sstabellini@kernel.org; Paul Durrant <Paul.Durrant@citrix.com>; Juergen
> >> Gross <jgross@suse.com>
> >> Subject: [PATCH v2] configure: use pkg-config for obtaining xen version
> >>
> >> Instead of trying to guess the Xen version to use by compiling various
> >> test programs first just ask the system via pkg-config. Only if it
> >> can't return the version fall back to the test program scheme.
> >>
> >> If configure is being called with dedicated flags for the Xen libraries
> >> use those instead of the pkg-config output. This will avoid breaking
> >> an in-tree Xen build of an old Xen version while a new Xen version is
> >> installed on the build machine: pkg-config would pick up the installed
> >> Xen config files as the Xen tree wouldn't contain any of them.
> >>
> >> Signed-off-by: Juergen Gross <jgross@suse.com>
> >> ---
> >> V2: - use pkg-config only if no Xen library paths have been specified via
> >>       --extra-ldflags
> >>     - keep test program for detecting Xen 4.9
> >
> > This all looks plausible but it doesn't seem to be working for me when
> trying to build 4.8. I'm still getting a xen ctrl version of 40900... still trying to
> figure out why.
> 
> I suppose you reverted my previous patch?
> 

Yes, I reverted that then applied this one.

> Do you happen to have some stale 4.9 libraries in your Xen tree?
>

Yes, it was picking up a libxendevicemodel when it should not have been. It would be handy if the probe compilations used --nostdlib, but that's not regression introduced by your patch. Now that pkg-config is used for out-of-tree builds I guess it may be possible to add that though.
 
> What happens without this patch?
> 
> > Also, the whitespace changes later on in the patch should probably be split
> out.
> 
> Hmm, those are just due to the nesting level of the if's changed.
> I don't think they can easily be split out without having a
> malformed indentation.
> 

Ok, I see that now I look at the code rather than just the patch. So, having fixed my linkage issue...

Tested-by: Paul Durrant <paul.durrant@citrix.com>

> 
> Juergen