Re: [PATCH] libxl: Fix building libxlu_cfg_y.y with bison 3.0

[Ian Campbell <Ian.Campbell@citrix.com>]

On Wed, 2014-12-10 at 11:41 -0500, Konrad Rzeszutek Wilk wrote:
> On Tue, Dec 09, 2014 at 03:25:29PM +0000, Ian Jackson wrote:
> > Ian Campbell writes ("Re: [Xen-devel] [PATCH] libxl: Fix building libxlu_cfg_y.y with bison 3.0"):
> > > There was a point in time where the prevailing version of bison (or
> > > maybe flex) in stable distro releases had a bug which meant these files
> > > could not be regenerated easily on common distros. I don't recall the
> > > details well enough to know if that time has now passed. Perhaps Ian J
> > > does.
> > 
> > We use (essential) features found only in non-ancient versions of
> > bison and flex.  The last time it was proposed to remove these
> > pregenerated files, there were complaints from people who were using
> > six-year-old bison and flex.
> > 
> > I think we should prioritise compatibility with new versions of bison
> > and flex, and retain the pregenerated versions of people with
> > incompatibly old version.
> > 
> > I think for 4.5 we should:
> > 
> >  * Regenerate the flex files with current wheezy's flex.  (I have
> >    reviewed the diff in the generated code.  It produces trivial
> >    changes which add declarations of xlu__cfg_yyget_column and
> >    xlu__cfg_yyset_column, but no code body changes - see below.)
> > 
> >  * Take the patch from Ed and regenerate the bison files too.
> > 
> > 
> > Konrad: can we have two freeze exceptions please ?
> > 
> > Risk analysis for Ed's patch:
> > 
> > Not taking the patch hurts systems with bison 2.7.1 or later:
> > 
> >   - Affected systems include Debian jessie, which will be
> >     released during the lifetime of 4.5.
> 
> My understanding is that Jessie won't be using Xen 4.5 but Xen 4.4 And the
> next version of Debian that will be released will be most likely using Xen 4.6.

What Jessie (or Fedora etc) has available in packages has no real
bearing on whether people might run Xen 4.5 on them, plenty of people
will still build from source, including developers.

Ian.