Behind this eye-catching title is an extension called blackhole that I implemented yesterday, tired of needing to always structure a fresh extension when needing one (well copying one from Postgres contrib/ would be fine as well). Similarly to blackhole_fdw that is aimed to be an extension for a foreign-data wrapper, blackhole is an extension wanted as minimalistic as possible that can be used as a base template to develop a Postgres extension in C.
When using it for your own extension, simply copy its code, create a new git branch or whatever, and then replace the keyword blackhole by something you want in the code. Note as well that the following files need to be renamed:
blackhole--1.0.sql
blackhole.c
blackhole.control
Once installed in a vanilla state, this extension does not really do much, as it only contains a C function called blackhole, able to do the following non-fancy thing:
=# \dx+ blackhole
Objects in extension "blackhole"
Object Description
----------------------
function blackhole()
(1 row)
=# SELECT blackhole();
blackhole
-----------
null
(1 row)
Yes it simply returns a NULL string.
The code of this template is available here, or blackhole/ with the rest of a set of PostgreSQL plugins managed in the repository pg_plugins. Hope that's useful (or not). In case, if you have ideas to improve it, feel free to send a pull request, but let's keep it as small as possible.
And Happy Halloween!