Re: [PATCH] CodingGuidelines: give deadline for "for (int i = 0; ..."

From: Phillip Wood <phillip.wood123@gmail.com>
Date: Mar 31, 2022, 14:48 UTC
Message-ID: <bf44f83b-0d18-8132-58cf-13155bfec40e@gmail.com>
In-Reply-To: <220331.86v8vuqv95.gmgdl@evledraar.gmail.com>

On 31/03/2022 11:10, Ævar Arnfjörð Bjarmason wrote:

Show 25 quoted lines

> 
> 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.

Show 21 quoted lines

> 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

Show 9 quoted lines

> 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.