[Pkg-fonts-devel] Possible abuse of dpkg-deb -z9 for xz compressed binary packages

Bastien ROUCARIES roucaries.bastien at gmail.com
Mon Sep 1 19:11:09 UTC 2014


Le 1 sept. 2014 14:21, "Guillem Jover" <guillem at debian.org> a écrit :
>
> Hi!
>
> I had noticed this a while ago while reading changelogs, but didn't
> realize at the time this poses actual problems, besides being possibly
> just a dubious practice.
>
> There seems to be some packages overriding the default compression
> level for xz to 9. This means dpkg-deb will require way more memory on
> both compression and decompression usually for extremely little gain,
> and might even fail on some systems with low memory (see #757740 for
> an example). But the real issue is that (as mentioned on the xz man
> page), using such high levels might actually make no sense at all
> when being using with data that is smaller than the dictionary size.
Could you fill a bug against lintian ?
> From doing a quick search on <http://codesearch.debian.net/> for
> “dpkg-deb.*-z9” and “dh_builddeb.*-z9”, but w/o looking in detail, it
> seems that most packages are or have been maintained by Daniel Baumann
> or the Fonts Team (both CCed). Was there an actual reason to use -z9,
> beside maybe trying to get the “bestest” compression possible? :)
>
> This could be checked from lintian by using something like:
>
>   $ ar x pkg.deb data.tar.xz
>   $ xz --list --verbose --verbose --robot data.tar.xz
>
> and comparing the file sizes with the dictionary size used. I'll be
> filing a bug report about this.
>
> Thanks,
> Guillem
>
>
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