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Re: [buildd-tools-devel] re buildd's resolver and package's build deps



On Wed, Feb 23, 2011 at 12:27:00PM +0200, Peter Pentchev wrote:
> Hi, and apologies in advance if this is a stupid question or if it has
> already been discussed :)
> 
> Is it possible that this should lead to problems with further levels of
> package dependencies?  E.g. something like that for two packages:
> 
> foo/control:
> Depends: bar-dev, libdb-dev | libdb4.7-dev
> 
> bar-dev/control:
> Depends: libdb4.7-dev
> 
> I realize that this is a somewhat contrived case, but still... wouldn't
> it break, or would that be considered a bug in the packages'
> dependencies?

If only the first alternative is considered, it will break.  apt-get
will not be able to install libdb-dev and libdb4.7-dev in parallel,
and so the build will be terminated due to unsatisfiable build
dependencies.  This isn't at all contrived; I saw many real examples
of this when doing the whole-archive rebuild, though thankfully 
actual breakage was extremely rare/nonexistent.

If alternatives are allowed, it will work out that libdb4.7-dev only
is acceptable and install just that.

> If the latter, well, wouldn't this leave the maintainer
> of foo a bit vulnerable against random decisions by the maintainers of
> bar-dev?

Very much so.  This is why library transitions need coordination,
since they have distribution-wide impact.  This is also a good
example of why we should aim to only have one major version of each
library in use at one time.


Regards,
Roger

-- 
  .''`.  Roger Leigh
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