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Re: Please test gzip -9n - related to dpkg with multiarch support

On Wed, Feb 08, 2012 at 03:06:46PM +0100, Adam Borowski wrote:
> gzip's output is likely to change:
> * on a new version
> * after a bugfix (including security ones)
> * on a different architecture
> * with different optimizations
> * with a different implementation (like those parallel ones)
> * possibly with a different moon phase
> Especially the first is pretty guaranteed to bite: whenever the upstream
> does a small improvement, binaries in the archive get invalidated until
> rebuilt with the new gzip.

Checking with a of 82613 files, compressing each file with gzip -n9 $file
resulted exactly same result with gzip of oldstable (2008) and gzip of
sid (2012).

Picking up woody gzip and libc from archive.debian.org (2002), 33 files were
not identical. This a 0.04% chance of differing file over a DECADE of changes.
While evidently changes do happen, certainly not a case of whenever a butterly
flaps wings in a certain direction gzip compression results change.

specifics of the the test setup:

2012 sid setup,   gzip 1.4-2, eglibc 2.13-20, built with gcc 4.6.1 amd64 binaries
2008 lenny setup, gzip 1.3.12-6+lenny1, glibc6 2.7-18lenny7, built with gcc 4.3, i386 binaries
2002 woody setup, gzip 1.2.4-33.1, glibc6 2.1.3-20, probably built with gcc 3.0, i386 binaries (duh)

Corpus of files was all the gzip compressed files extracted and uncompressed
from a partial debian mirror. 

All tests during the current almost full moon phase.


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