Date: Sun, 13 Sep 2009 11:37:46 +0100 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Jos Chrispijn <kernel@webrz.net> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: Perl updates Message-ID: <4AACCB7A.2050106@infracaninophile.co.uk> In-Reply-To: <4AACBF63.8020304@webrz.net> References: <4AACBF63.8020304@webrz.net>
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Jos Chrispijn wrote:
> Can someone explain why we have to run an update batch in order to have=
=20
> all Perl related programs running with this update? Wouldn't it be=20
> better to upgrade Perl and have all programs use it as it hadn't been=20
> updated at all?
You're talking about the update of lang/perl5.10 from perl-5.10.0
to perl-5.10.1 ?
The reason you need to run perl-after-upgrade is because perl library
modules are stored in directory trees which encode the perl version numbe=
r.
perl-after-upgrade basically moves installed modules from
/usr/local/lib/perl5/site_perl/5.10.0=20
to
/usr/local/lib/perl5/site_perl/5.10.1
plus it fixes up all of the pkg-plists and various other places where
the directory path is embedded. Alternatively you could just re-install
every single perl module on the system, plus any other ports that depend
on perl, but that's going to be the majority of the software on your mach=
ine
and perl-after-upgrade is a lot quicker.
Even so, ports that embed a perl interpreter -- ie. that dynamically link=
against libperl.so -- will need to be recompiled, to account for libperl.=
so
now being in a different location. There aren't too many of these:
net-mgmt/net-snmp and www/mod_perl{,2} are probably the most commonly
encountered. One of the functions of perl-after-upgrade is to tell you w=
hat
packages need to be rebuilt because of this.
Why isn't perl-after-upgrade run automatically? Two reasons. Firstly, th=
e
ports system cannot itself distinguish what updates would require
perl-after-upgrade to be run: when updating, the mechanism is to delete =
the
old package and then install the new one as if de-novo. The newly instal=
led
package has no information about what older version of itself it is repla=
cing,
if any.
Secondly, you can't make perl-after-upgrade clever enough to deal with al=
l
conceivable corner cases. Other than by enforcing particular usage rules=
on how individual admins manage their perl installations -- a policy that=
is manifestly *not the BSD way* -- this is unfeasible. Given that we hol=
d that
it is in the gift of the individual admin to decide how to manage their s=
ystems,
there have to be stages somewhere that involve the admin making a conciou=
s
decision about what to do. Running perl-after-upgrade is one of those po=
ints.
Lastly, just to note that if the upgrade is across a significantly large =
change
in version number: eg from perl-5.8 to perl-5.10, then any dynamically lo=
aded
compiled extension modules (see perlxs(1)) will have to be recompiled as =
the
ABI is not guaranteed to be kept the same in that case. Unfortunately,
distinguishing modules that use perlxs from pure perl modules is not some=
thing
the ports system is currently capable of, so the upgrade instructions the=
re are
"rebuild everything that depends on perl".
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
Kent, CT11 9PW
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