Re: [PATCH] hg ignore libxl lex/yacc detritus

[Ian Jackson <Ian.Jackson@eu.citrix.com>]

Keir Fraser writes ("Re: [Xen-devel] [PATCH] hg ignore libxl lex/yacc detritus"):
> My preference would be to delete the checked-in generated files. Then either
> declare old flex/bison to be simply unsupported, or avoid depending on
> whatever feature it is that is not supported in those old flex/bison
> versions. Checking in the generated output is a cheap hack workaround.

I think what we have now is a good compromise.  If you have working
flex and bison then everything works absolutely fine; if we update the
input files we have to remember to run make before committing but
that's not hard (and I do a build test anyway).

However providing the checked-in files means that people who have
crazy prehistoric versions of flex (1993 in the case of RHEL5 AIUI) or
whatever can still build the system.  If they work in xen-unstable
they may need to knock make on the head, but at least they have a
workaround.  If we didn't provide the generated files checked-in,
the workaround would be much worse.

As an aside, I think there is generally nothing wrong in principle
with checking in generated files.  It's something that should be done
with proper thought and care, but it's often appropriate.  Eg,
automake-using systems should contain configure and configure.in and
Makefile.in, so that people who don't have the right version of
automake can still build from a checkout.

Ian.