[postgis-devel] liblwgeom symbols exported by postgis module

[Stephen Frost]

* Sandro Santilli (strk at keybit.net) wrote:
> Doing this I've discovered that the linux runtime environment can get
> confused about where to find a given symbol, so that _some_ functions
> are really served by the liblwgeom library that was found at build
> time and some others are served by the liblwgeom library embedded
> in the PostGIS module (loaded by the same PostgreSQL backend process).

Yeah, many libraries suffer from this problem..

> One way to fix this "clash" would be to build the PostGIS module so
> to _not_ re-export symbols imported from the libraries it depends to.
> I think this is a good thing to do, to reduce noise/confusion/size;
> when using the GNU linker, "--exclude-libs ALL" switch can be used
> for that, and a patch to that extent can be found starting from here:
> https://trac.osgeo.org/postgis/ticket/3281
> 
> Another way might be to build the new (first versioned) liblwgeom
> with symbol level versioning, but I hadn't tried that.

The people to discuss this with, really, are the Debian library folks.
Last I checked, symbol versioning was the 'right' answer and there were
issues with more-or-less all other approaches, but that was a while ago.

> Finally, last possibility is to just give up on dynamically linking
> the PostgreSQL module to liblwgeom and follow the static-link route
> also taken by PostGIS, which means, if I'm not mistaken, also having
> to deal with linking all of the liblwgeom dependencies
> (GEOS, PROJ, SFCGAL).

That's not going to fly for Debian and other distributions.

> While I know Paul and Regina will be laughing on me on this,
> is there anyone with ideas on what the best way to deal with
> these static-linking pollution matters ?

I'd strongly suggest talking to the Debian people, Steve Langasek in
particular.  You might also try #debian-devel on OFTC.  Quite a few
people who are smart on these things hang out there.

Thanks!

Stephen
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