Re: Avoid circular header file dependency

Bertrand Drouvot <bertranddrouvot.pg@gmail.com> writes:
> While working on wait events I faced some compilation issues due to circular
> header file dependency (introduced in fa88928470b5) between wait_event.h and
> wait_event_types.h.

Ugh.  I still carry the scars of cleaning up after a previous
circular-inclusion mess (cf 1609797c2), so I'm always worried about
introducing new cases.  I don't have an opinion about whether this
specific refactoring is the best way to deal with this case, but
I definitely feel that we mustn't allow the situation to persist.

> Out of curiosity, I ran clang-tidy with misc-header-include-cycle ([1]) and it
> also reports:
> ../src/pl/plpython/plpy_util.h:9:10: warning: circular header file dependency detected while including 'plpython.h'
> This one worries me less because plpy_util.h only contains simple external
> function declarations.

Whatever it contains, we need to kill it with fire before the problem
metastasizes like it did the last time.  (yeah, yeah, badly mixed
metaphors)  I can take a look at this one over the weekend if nobody
beats me to it.

I am very glad to hear that there's a readily available tool to
catch such cases.  We ought to run it every so often.

            regards, tom lane