From: Phillip Wood Date: Thu, 31 Mar 2022 14:48:56 GMT Subject: Re: [PATCH] CodingGuidelines: give deadline for "for (int i = 0; ..." Message-ID: In-Reply-To: <220331.86v8vuqv95.gmgdl@evledraar.gmail.com> On 31/03/2022 11:10, Ævar Arnfjörð Bjarmason wrote: > > On Wed, Mar 30 2022, Junio C Hamano wrote: > >> We raised the weather balloon to see if we can allow the construct >> in 44ba10d6 (revision: use C99 declaration of variable in for() >> loop, 2021-11-14), which was shipped as a part of Git v2.35. >> Document that fact in the coding guidelines, and more importantly, >> give ourselves a deadline to revisit and update. >> >> Let's declare that we will officially adopt the variable declaration >> in the initializaiton [...] > > Typo: initialization. > >> part of "for ()" statement this winter, unless we find that a platform >> we care about does not grok it. > > I'd think that waiting a couple of releases would be sufficient for this > sort of thing. I.e. contributors to this project already have > access/knowledge about a wide variety of compilers, especially the > "usual suspects" (mainly MSVC) that have been blockers for using new > language features in the past. > > So I'm in no rush to use this, and the winter deadline sounds fine to > me in that regard. Agreed, I think it is worth waiting so we don't get into a situation where we end up having to revert changes that are using the new features because we discover they are not supported by a platform we care about. > But on the other hand I think the likelihood that waiting until November > v.s. May revealing that a hitherto unknown compiler or platform has > issues with a new language feature is vanishingly small. > >> A separate weather balloon for C99 as a whole was raised separately >> in 7bc341e2 (git-compat-util: add a test balloon for C99 support, >> 2021-12-01). Hopefully, as we find out that all C99 features are OK >> on all platforms we care about, we can stop probing the features we >> want one-by-one like this > > Unfortunately this really isn't the case at all, the norm is for > compilers to advertise that they support verison X of the standard via > these macros when they consider the support "good enough", but while > there's still a long list of unimplemented features before they're at > 100% support (and most never fully get to 100%). > > We also need to worry about the stdlib implementation, and not just the > compiler, see e.g. the %zu format and MinGW in the exchange at > https://lore.kernel.org/git/220318.86bky3cr8j.gmgdl@evledraar.gmail.com/ > and > https://lore.kernel.org/git/a67e0fd8-4a14-16c9-9b57-3430440ef93c@gmail.com/; That's a good point, it was a surprise to me that the problem is with MinGW rather than MSVC. Best Wishes Phillip > But I think we're thoroughly past needing to worry about basic language > features in C99 such as these inline variable declarations. > >> (it does not necessarily mean that we would automatically start using >> any and all C99 language features, though). > > Yes, particularly those that the standards committee backed out of or > made optional after C99 would be good candidates for avoiding > permanently.