Weston versioning (Re: [PATCH weston 6/6] libweston: do not use weston version in libweston.pc)

[Pekka Paalanen]

On Sun, 10 Jul 2016 14:34:28 +0200 (CEST)
Jan Engelhardt <jengelh at inai.de> wrote:

> On Sunday 2016-07-10 13:13, Quentin Glidic wrote:
> >
> > If we install only one .pc file:
> > - You cannot develop against an old version.  
> 
> I do not feel that is true. If you have Berkeley DB 4.5 in tarball
> form, you can build and `make install` it. Provided the SONAME is
> different (it is; libdb-4.5.so), it *ought* not to break the rest of
> your system which relies on libdb-4.8.so.
> 
> If you have db 4.5 in distropackage form, you can install the
> libdb-4_5.rpm library, and it won't kick out libdb-4_8, and you can
> install libdb-4_5-devel.rpm, which only kicks out libdb-4_8-devel,
> but that is a negligible fact, as distro build results show that
> no one seriously needs 4.5 and 4.8 at the same time a particular
> software component is built.
> 
> The example extends to packages other than bdb. (bdb has no .pc
> file, which is the same complexity class a one .pc file.)

Hi Jan,

I think Quentin raised a good point, though. In source-based
distros, well, in Gentoo at least which I use almost exclusively,
there are no separate -devel packages.

I haven't even looked at how Gentoo would solve the issue where you
cannot install multiple versions of library headers to allow
installing (which implies building from source) two different
programs each depending on the different version of the library and
headers.

Would it be so bad to assume that compositor projects would not
bother supporting more than one (or few at most) libweston MAJOR at
a time?

OTOH, would adding a new libweston MAJOR in an already stable and
released binary distribution be absolutely forbidden? It would by
definition not affect anything the distribution was released with,
unless libweston's dependencies changed, but I think the
dependencies might change less often than we bump MAJOR.

I believe the burden of adding pkg-config checks will be
insignificant compared to the work needed for a compositor project
to actually work with multiple libweston MAJORs.

It's good have a seasoned packager like you (thanks for the
introduction, puts your comments in whole different perspective for
me!) to comment on these things. There are more issues I'd like
someone to sanity-check after this versioning issue gets resolved.
It would essentially boil down to checking Weston's README for the
packager notes if they make sense as a plan, and what we could do to
help packaging.

In summary, the only downside from installing all devel files
MAJOR-specific is that user projects need multiple pkg-config
checks if they want to support multiple MAJORs, right?

I'd vote for taking that hit and seeing if anyone complains loud
enough.


Thanks,
pq
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