Re: [gentoo-dev] [RFC] Policy for migrating library consumers to subslots

[Ian Stakenvicius]

On 2013-09-28, at 9:43 AM, Davide Pesavento <pesa@g.o> wrote:

> On Fri, Sep 27, 2013 at 4:44 PM, Michał Górny <mgorny@g.o> wrote:
>> Dnia 2013-09-26, o godz. 17:24:49
>> Davide Pesavento <pesa@g.o> napisał(a):
>>
>>> On Thu, Sep 26, 2013 at 4:04 PM, Kent Fredric <kentfredric@×××××.com> wrote:
>>>>
>>>> On 26 September 2013 19:53, Michał Górny <mgorny@g.o> wrote:
>>>>>
>>>>> How do we handle packages which install multiple libraries? I'm afraid
>>>>> forcing such a policy and/or hurrying developers to adapt will only
>>>>> cause more of poppler-like issues to occur.
>>>>
>>>>
>>>> Can you give a an example package which:
>>>>
>>>> - installs multiple libraries
>>>> - has an ABI that may change for only one of those libraries
>>>> - it is sane / plausible to expect one downstream dependent *not* to
>>>> forcibly rebuild as a result of a chane in one of those libaries
>>>> - it is sane / plausible to expect a different downstream to forcibly
>>>> rebuild as a result of changes in one of those libraries
>>>
>>> dev-python/PyQt4
>>>
>>> Each module is a separate library, and each has its own ABI that can
>>> change independently from the others. Downstream projects that rely
>>> only on PyQt4's python API are not affected by ABI changes, but those
>>> (very few) that link against one or more modules (e.g. kde-base/pykde4
>>> I think) must be rebuilt.
>>
>> How often does ABI of pyqt4 libraries change in such a way that rebuild
>> of pykde4 is not required?
>
> Practically never (see below).
>
>>
>> Looking at the dep:
>>
>>> =dev-python/PyQt4-4.9.5[${PYTHON_USEDEP},dbus,declarative,script(+),sql,svg,webkit,X]
>>
>> I'd think it's fairly rare when only the libraries not listed above
>> change ABI without any of the remaining ones changing it.
>
> Actually, most PyQt4 libraries never changed their ABIs since the
> initial 4.0 release, so yes, it's "fairly rare" :)
> That's also one of the reasons why I never bothered to add a subslot to PyQt4.
>
> Thanks,
> Davide
>


it is very important to note that slot operators should be used even when the atom is unlikely to ever bump ABI or SONAME.  it is the rare big update that breaks everything -- think the expat update fiasco from a few years back.