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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Dec 10, 2014 at 04:44:00PM +0000, Ian Campbell wrote:
> 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.

My initial reasoning for not giving the exception was that this bug did
not affect users.

But it does affect developers and distros - which in number comparison to
users make a miniscule amount.

However, from an perspective of bug-fixing, they (developers) are the most
important - not users. Hence making the environement for them to fix issues
and develop new features without much fuss is paramount. As in, I do not want
them to start looking at fixing an issue/developing, and this crops up and
they say "WTF? I just want to add this tiny libxl feature and I get this!
This is a quagmire".

Based on that reasoning (And thank you for pointing out the developers
factors), I retract my earlier reason and:

Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

P.S.
And I just verified that this does not cause regressions with bison 2.4.1, so
that is OK.

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