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Re: G++ 2 => 3 transition (was Re: GNU C++ 3.0 porting help wanted)

Sean Middleditch writes:
> Richard Kettlewell wrote:

>> You appear be seriously proposing to that Debian distribute, at
>> different times, libraries with different ABIs but with the same
>> name and version number.  (Correct me if I'm wrong.)
> I would imagine that the Debian packages could be updated (libabc4
> to libabc5, etc.).

(It is the filename and version of the library that is important, not
that of the package.)

>> Firstly, this will break any Debian package that depends on the old
>> libraries but is not upgraded when the new ones are installed.  An
>> example of such a package would be one no longer in the distribution
>> at the time the new libraries are added.
> All the other solutions cause breakage in some other way.

What breakage will follow from creating a new version number for the
new-ABI library?

(Incompatibility between distributions is only a problem here if this
approach is followed wrongly, i.e. without some sort of coordination
with upstream.)

>> Secondly, not all software installed on all Debian systems came
>> from a Debian package: some of it was compiled locally.  If you
>> replace the libraries such software depends on with new versions
>> with the same name and version but incompatible ABIs then that
>> software will break.
> How else can this be avoided?  We could have two versions of the
> libs installed, but that will cause all sorts of other problems.
> Both archive size will greatly increase,

Huh?  Archive size only increases if you distribute both the old and
the new versions.

> plus if upstream doesn't change version numbers, we won't be able to
> have both versions installed anyways.

If upstream refuse to change the version number when they change the
ABI then that should be treated the same as any other upstream action
that makes it impossible to package something for Debian.  In practice
I doubt this will happen if someone takes the time to explain the
problem to any upstream authors who happen not to be aware of the

>> I don't see why anyone should accept a less-good solution for the
>> g++ 2->3 transition.
> Because of how many libraries there are to deal with.  Not just one
> core library, but now dozens and/or hundreds (haven't counted)
> libraries.

Huh?  Every single shared library had to be recompiled for the 4->5
and 5->6 transitions, not just the libc.


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