Needing perl to build perl

[Dominic Hargreaves]

On Mon, Jan 30, 2012 at 08:47:49AM +0200, Niko Tyni wrote:
> On Sat, Jan 28, 2012 at 05:37:35PM +0000, Dominic Hargreaves wrote:
>  
> > I spotted that although we don't use debhelper (I assumed that this was
> > to avoid bootstrapping problems building perl with perl available - but
> > maybe it's just that no-one's wanted to go through and modernise the rules
> > file) we do use a few utilities from dpkg-dev written in perl:
> 
> It definitely has to do with bootstrapping, quoting Brendan in #556847:
> 
> > Note that one of the reasons why perl has a slightly eccentric rules
> > file is so that the package is able to be built on a system without
> > any perl installed.  This was to allow new ports to bootstrap and is
> > the reason why ./perl.static is used in that file rather than
> > /usr/bin/perl.  It is entirely possible that bit-rot has made this no
> > longer work, but it is still a useful goal to retain.
> > 
> > See debian/checkperl, which is invoked for the install rule.
> 
> I believe the perl scripts in dpkg-dev are the primary cause for
> the bit-rot.  However, I don't think we can hardcode things like
> './perl.static /usr/bin/dpkg-architecture' in debian/rules, because of:
> 
> - ABI skew when building a different major version than
>   the one on the system: any XS modules that dpkg-architecture might
>   load would not work with the perl we're building.
> 
> - we can't really know if /usr/bin/dpkg-architecture turns
>   into a compiled binary or a python script in the next dpkg-dev version.
> 
> > debian/config.debian:
> > - dpkg-architecture
> > 
> > debian/rules:
> > - dpkg-parsechangelog
> > - dpkg-gencontrol
> > - dpkg-shlibdeps
> 
> > My question is, I suppose: is there any reason not to start using
> > another perl script from dpkg-dev in the rules file, or should we be
> > aspiring not to require perl to build perl?
> 
> I don't see how adding dpkg-buildflags would make the situation any worse
> than it currently is, though ideas for improving this area would be welcome.

Yep, thanks for the background. I've added a comment to the rule file
explaining this with a pointer back to this thread. No ideas at the 
moment.

It does occur to me that practically speaking, people must be managing,
since several new architectures have been bootstrapped recently.

Cheers,
Dominic.

-- 
Dominic Hargreaves | http://www.larted.org.uk/~dom/
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