Re: [Xen-devel] [PATCH 4.4 2/2] libxl: Fix building libxlu_cfg_y.y with bison 3.0

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2016-01-06 at 02:10 -0700, Jan Beulich wrote:
> > > > On 04.01.16 at 15:50, <ian.jackson@xxxxxxxxxxxxx> wrote:
> > From: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
> > 
> > - Use %lex-param instead of obsolete YYLEX_PARAM to override lex
> > scanner
> > Â parameter
> > - Change deprecated %name-prefix= to %name-prefix
> > 
> > Tested against bison 2.4.1 and 3.0.2.
> > 
> > This is expected to sometimes (depending on timestamps and whether the
> > bison input files are edited) break building on systems with ancient
> > versions of bison.ÂÂBison 2.4.1 is known to work and was released in
> > December 2008.
> > 
> > Also, consquentially, regenerate bison output files with bison
> > 1:2.5.dfsg-2.1 from Debian wheezy.
> > 
> > Signed-off-by: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
> > Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > Tested-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> > Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > 
> > (cherry picked from commit 7ba4cdfadd4f3c45d65ffe50e621759f458fedc0)
> > 
> > [ I have checked that rebuilding the bison and flex input produces no
> > Â further changes. -iwj ]
> > 
> > Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> 
> Well, as indicated already when the original change went in, a
> statement of compatibility back to a bison released in 2008 is
> fine, but not really sufficient considering that e.g. compiler and
> and binutils are permitted to older. I stopped objecting to the
> change for -unstable at that time, but I'm not sure we want to
> introduce such an incompatibility (the %name-prefix change)
> with older bison in a wrap-up release. In the end the question
> certainly is whether updating the build host distro for released
> branches is a proper thing to do.

The outputs are checked in, which mitigates things somewhat since you
wouldn't expect bison to actually be run unless you had edited the input
files.

I suspect that in reality it is run needlessly in some cases, I'd say we
should either fix that (might be hard, since it involves VCS setting timestamps 
consistently) or at least provide a manual "never run bison" switch.

Ian.

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