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Bug#718297: Bug#718295: /usr/bin/dpkg-deb: dpkg-deb -Zgzip -z0 produces invalid debian packages



On Mon, 2013-07-29 at 22:54 +0200, Guillem Jover wrote:
> Hi!
> 
> On Mon, 2013-07-29 at 21:33:36 +0200, Helmut Grohne wrote:
> > Package: dpkg
> > Version: 1.17.0
> > Severity: important
> > File: /usr/bin/dpkg-deb
> 
> > The linux maintainers chose to pass -Zgzip -z0 to dpkg-deb to retain
> > backwards compatibility.
> 
> To retain compatibility they should either not have specified -z at all
> or used -z9. dpkg-deb(1) is pretty clear that -z0 for gzip is equivalent
> to no compression.

That was the intent.  This is used only for the linux-source-3.10
package (and its successors), which contain xz-compressed files and are
therefore not significantly compressible.  All our other binary packages
use xz compression.

> > Unfortunately the resulting binary package does
> > not conform to the format documented at man 5 deb. It contains a
> > data.tar.gz memeber, that is not a valid gzip file. dpkg-deb should
> > produce the correct extension for uncompressed data members.
> 
> Ah right, although zlib handles the no compression part just fine, so
> does «gzip -f». In any case I've to say I've always kind of wondered
> about the usefulness of -z0 for gzip, because it's an ofuscated way
> to just say -Znone.

Unfortunately dak (and presumably other tools) do not accept compression
of 'none'.  This workaround was suggested when I asked on #debian-ftp.

Ben.

> At this point I'm tempted to just deprecate -Zgzip -z0. I'll fix this
> in any way for 1.17.2.

-- 
Ben Hutchings
Quantity is no substitute for quality, but it's the only one we've got.

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