Re: [PATCH 2/2] ci: let pedantic job compile with -Og

From: Jeff King <peff@peff.net>
Date: Jun 6, 2024, 08:05 UTC
Message-ID: <20240606080552.GA658959@coredump.intra.peff.net>
In-Reply-To: <ZmFoRPd52iqxbOTJ@tanuki>

On Thu, Jun 06, 2024 at 09:41:56AM +0200, Patrick Steinhardt wrote:

Show 8 quoted lines

> > If we want to get coverage of -Og, I'd suggest doing it in a job that is
> > otherwise overlapping with another (maybe linux-TEST-vars, which I think
> > is otherwise a duplicate build?).
> 
> I don't think linux-TEST-vars would be a good candidate for this because
> it uses Ubuntu 20.04. Ideally, we'd want to have a test run with an
> up-to-date version of Ubuntu so that we also get a recent version of the
> compiler toolchain.

Oof, yeah, I agree that if the point is to find obscure warnings, newer is going to be better.

Show 6 quoted lines

> I kind of wonder whether we should revamp this pedantic job in the first
> place. The consequence of that job is that our codebase needs to be
> compile cleanly with `-Wpedantic`. So if that is a requirement anyway,
> why don't we run all jobs with `DEVOPTS=pedantic` and just drop this job
> altogether? This may surface some additional warnings on platforms where
> we currently don't set that, but is that a bad thing?

Yeah, if we always compile cleanly with pedantic, then I don't see why it wouldn't just be the default for DEVELOPER=1. The point of that flag is to be as picky as possible so that we catch things early. If some platform can't handle it (let's imagine Windows or something), then I think we should be explicitly _disabling_ pedantic there.

Show 5 quoted lines

> The only downside I can think of is that we stop compiling on Fedora,
> which may have a more up-to-date GCC version than Ubuntu. But if the
> goal of this job was to _really_ get an up-to-date compiler toolchain,
> then we should rather pick a rolling release distro like Arch. Otherwise
> I find this to be of dubious benefit.

There may be some value in general in compiling on multiple distros, as a sort of "unknown unknowns" thing. We don't know what we might turn up, but exposing ourselves to more variables may lead to catching failures before users see them.

I don't know if Fedora was specifically chosen for recent gcc there, or if it was simply for variety.

Once again, these overlapping variables within various jobs make it hard to reason about (but I don't propose normalizing all of them; that would increase the amount of CPU work by a lot; I am just grumbling).

But yeah, between Arch and Fedora, I don't have an opinion. Doing both might even be valuable, if we are shoving random variations into random jobs. ;)

> If we merge it into the other jobs, then I'd just pick any random job
> that uses "ubuntu:latest" like "linux-gcc-default" to compile with
> `-Og`.

That would be OK with me. I also think it would be OK to do nothing for now. We saw one case where "-Og" found a warning that "-O2" didn't. We could wait to see if it happens twice before acting. I dunno.

-Peff