Re: [Qemu-devel] [PATCH 09/21] configure: use pkg-config for obtaining xen version

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Dec 11, 2018 at 10:34:52AM +0000, Peter Maydell wrote:
> On Tue, 25 Apr 2017 at 19:35, Stefano Stabellini <sstabellini@kernel.org> wrote:
> >
> > From: Juergen Gross <jgross@suse.com>
> >
> > 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>
> > Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
> > Tested-by: Paul Durrant <paul.durrant@citrix.com>
> > Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> > ---
> >  configure | 159 ++++++++++++++++++++++++++++++++++----------------------------
> >  1 file changed, 88 insertions(+), 71 deletions(-)
> >
> > diff --git a/configure b/configure
> > index 271bea8..3133ef8 100755
> > --- a/configure
> > +++ b/configure
> > @@ -1975,30 +1975,46 @@ fi
> >  # xen probe
> >
> >  if test "$xen" != "no" ; then
> > -  xen_libs="-lxenstore -lxenctrl -lxenguest"
> > -  xen_stable_libs="-lxencall -lxenforeignmemory -lxengnttab -lxenevtchn"
> > +  # Check whether Xen library path is specified via --extra-ldflags to avoid
> > +  # overriding this setting with pkg-config output. If not, try pkg-config
> > +  # to obtain all needed flags.
> > +
> > +  if ! echo $EXTRA_LDFLAGS | grep tools/libxc > /dev/null && \
> > +     $pkg_config --exists xencontrol ; then
> > +    xen_ctrl_version="$(printf '%d%02d%02d' \
> > +      $($pkg_config --modversion xencontrol | sed 's/\./ /g') )"
> > +    xen=yes
> > +    xen_pc="xencontrol xenstore xenguest xenforeignmemory xengnttab"
> > +    xen_pc="$xen_pc xenevtchn xendevicemodel"
> > +    QEMU_CFLAGS="$QEMU_CFLAGS $($pkg_config --cflags $xen_pc)"
> > +    libs_softmmu="$($pkg_config --libs $xen_pc) $libs_softmmu"
> > +    LDFLAGS="$($pkg_config --libs $xen_pc) $LDFLAGS"
> > +  else
> 
> Hi -- this is an old patch, but MJT has just noticed that
> it means that (assuming configure takes the "we have a pkg-config
> for Xen" path) the Xen libraries get added to both libs_softmmu
> and LDFLAGS, which means that everything, including the linux-user
> binaries, gets linked against them. The old fallback path
> only adds them to libs_softmmu.
> 
> Juergen: is there a reason why you added the libs to both
> libs_softmmu and LDFLAGS here? Can we just delete the line
> that alters LDFLAGS?

In the 'else' block that takes the non-pkg-config path, the libs are
only added to "libs_softmmu". So I think removing LDFLAGS is right.

Regards,
Daniel
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