Re: Should contrib modules install .h files?

On 2 July 2018 at 02:23, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> wrote:

> So I have this immediate problem: a PGXS build of a module, specifically
> an hstore transform for a non-core PL, is much harder than it should be
> because it has no way to get at hstore.h since that file is never
> installed anywhere.
>
> Should that be changed?
>
>
I think there's agreement in the thread that it should, and strong +1 from
me.

I just wanted to pipe up with something Petr pointed out during pglogical
development, which is that Pg offers a handy tool to help extensions link
up with each other - find_rendezvous_variable(...) from dfmgr.c / fmgr.h .

It's a real shame it's not more visible in contrib/ examples and the docs.
Any suggestions on where it should appear in the docs? Somewhere in
extend.sgml, presumably.

You still need a header from the other extension to *use* it, but it
provides a massively easier way to find a struct of API function pointers.
Prior to using it, I had a hack where I dlopen()ed the other shared library
directly, and I'd also trialled using the fmgr to call a 'returns internal'
function to get the API pointers struct that way.

--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services