[postgis-devel] liblwgeom versioning

[Sandro Santilli]

On Thu, Oct 08, 2015 at 08:53:37AM -0400, Greg Troxel wrote:
> Sandro Santilli <strk at keybit.net> writes:

> Ah, now I get it.  You are talking about having liblwgeom-X.Y.so for
> postgis X.Y.  That will result in an ABI break on update to postgis 2.3
> for anything that actually depends on liblwgeom.  There will presumably
> not be that many, so that's probably ok.

Exactly. Consider we're coming from having liblwgeom-X.Y.Z.so,
so this is actually an evolution :)

> I have trouble getting my head around the way that libtool wants sonames
> to be specified.  THe mechanism is probably to accomodate other than
> elf.   So I think it's helfpul to talk about the ELF versions and then
> reverse engineer the libtool codes.

I think it would be very helpful to have access to non-ELF systems
to see if the 3:0:0 versioning should be changed to be 5:0:0 instead
(coming from 4:2:0)

> Do you expect there to be an ABI break in liblwgeom in every postgis
> major (e.g. 2.2 to 2.3) release?

Not necessarely, but since liblwgeom is shipped with postgis, rather
than having its own release cycle, keeping it bound to the PostGIS
branch name (Major.Minor) is to reduce headaches...

> Do you expect postgis packages to include liblwgeom?  Or do you expect
> there to be a separate liblwgeom?  If the latter, there should be an
> easy way (configure flags, or separate directory in the tarball) to
> build just liblwgeom, and then to expect the postgis build to look for
> an use an installed liblwgeom.  Basically my point is either that it's
> part of postgis or it isn't (either is fine), and there is no middle
> ground without a lot of special-case pain.

Source packages will include liblwgeom, but I expect binary packages to
ship liblwgeom separately. Starting with 2.2.0 (released tonight)
there is a way to build liblwgeom only:

  ./configure --without-pgconfig

The special-case _maintainance_ pain so far seems to be relieved by
including Major.Minor of PostGIS in the SONAME. I understand there's
still some _usage_ pain, but we have to find a balance...

--strk;

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