On Tue, Feb 23 2021, Jeff King wrote: > On Tue, Feb 23, 2021 at 12:41:32PM +0100, Ævar Arnfjörð Bjarmason wrote: > >> Adding $(FUZZ_OBJS) as a dependency on "all" was intentionally done in >> 5e472150800 (fuzz: add basic fuzz testing target., 2018-10-12). >> >> Rather than needlessly build these objects which aren't required for >> the build every time we make "all", let's instead move them to be >> built by the CI jobs. >> >> The goal is to make sure that we don't inadvertently break these, we >> can accomplish that goal by building them in CI, rather than slowing >> down every build of git for everyone everywhere. > > The current state is that regular devs are responsible for avoiding > compile breakages in the fuzz objects, even if they don't care > themselves. Your earlier patches turned this into: regular devs are not > on the hook for breaking fuzz objects; they are the responsibility of > fuzz people. I'm OK with either of those, but this approach seems to me > like the worst of both worlds. ;) > > If you do a refactor, you are still on the hook for breaking the fuzz > objects because CI will fail (and you have to investigate it, and fix it > for CI to remain a useful tool). But instead of finding out about the > problem quickly as you're working, instead you push up what you think is > a finished result, and then from minutes to hours later you get a > notification telling you that oops, you missed a spot. I find that the > shorter the error-fix-compile cycle is, the less time I waste waiting or > context-switching. > > If we had a ton of fuzz object files that took forever to build, the > savings on each build might be worth it. But AFAICT (from timing "make > clean; make -j1" before and after), we are saving less than 1% of the > build time (which is way less than the run-to-run noise). > > It doesn't seem like the right tradeoff to me. (Likewise, if other > CI-only checks we have, like coccinelle, could be run at a similar cost, > I'd recommend sticking them into the default developer build). It's mainly psychological and doesn't contribute much to overall build time as a percentage, but I find it grating that the last thing I see before I switch away from that terminal when firing off a build on a slower GCC farm box I can only use -j1 on, is these fuzz objects taking 2-3 seconds to build, knowing I'm wasting time on something I'll never need. I think when we build something we should narrowly be compiling only the things we need, not running some sort of pseudo-CI on every developer's computer. We can have CI or other targets for that. Besides, if we were going for some sane cost-benefit here we'd have targets to try compiling with NO_CURL=1 or some other conditional setups that are actually common in the wild. > One thing we _could_ do is stop building fuzz objects as part of "all", > but include them for DEVELOPER=1 builds (which includes CI). That keeps > them from hurting normal users (who don't actually need them), but > prevents bitrot. It doesn't address your original motivation though (you > as a developer would probably still be building them). Please no. A very good thing about how DEVELOPER=1 works is that we're not doing anything extra except advisory compilation flags. It's turned on for "production" builds in a lot of settings because of that. It would also be very annoying to e.g. have some failure on Solaris or whatever, debug it with DEVELOPER=1, and then get some completely unrelated failure in the developer-only code, e.g. because we'd decided to compile all of fuzz/NO_OPENSSL/NO_CURL etc. and had some bug there. Yes that bug would be worthwhile to fix, but not right there and then. So having it under some "make all-combinations" flag or whatever would be better.
