Re: [PATCH] CodingGuidelines: document test balloons in flight

[Junio C Hamano <gitster@pobox.com>]

Phillip Wood <phillip.wood123@gmail.com> writes:

> Hi Junio
>
> On 23/07/2025 20:31, Junio C Hamano wrote:
>> Due to portability concerns, we do not blindly say "It is in [[this
>> standard]], so we will make liberal use of it" for many features,
>> and use of C99 language features follow this same principle.  When
>> we contemplate adopting a language feature that we haven't used in
>> our codebase, we typically first raise a test balloon, which
>>   - is a piece of code that exercises the language feature we are
>>     trying to see if it is OK to adopt
>>   - is in a small section of code that we know everybody who cares
>>     about having a working Git must be compiling
>>   - is in a fairly stable part of the code, to allow reverting it
>>     easily if some platforms do not understand it yet.
>> After a few years, with no breakage report from the community, we'd
>> declare that the feature is now safe to use in our codebase.  Before
>> that, we forbid the use of the language construct except for the
>> designated test balloon code site.
>> The CodingGuidelines document lists these selected features that we
>> already have determined that they are safe, and also those features
>> that we know some platforms had trouble with.
>> Let's also start listing ongoing test balloons and expected timeline
>> for adoption.
>> Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>
> I'm not sure what I've done to deserve that - it was Patrick that
> pointed out the test balloon already existed. The patch and the commit
> message look good to me.

Let me assign equal credit to Patrick.  Thanks.

>> Signed-off-by: Junio C Hamano <gitster@pobox.com>
>> ---
>>   Documentation/CodingGuidelines | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>> diff --git a/Documentation/CodingGuidelines
>> b/Documentation/CodingGuidelines
>> index c1046abfb7..0776d15a95 100644
>> --- a/Documentation/CodingGuidelines
>> +++ b/Documentation/CodingGuidelines
>> @@ -298,6 +298,14 @@ For C programs:
>>      . since late 2021 with 44ba10d6, we have had variables declared in
>>        the for loop "for (int i = 0; i < 10; i++)".
>>   +   C99 features we have test balloons for:
>> +
>> +   . since late 2024 with v2.48.0-rc0~20, we have test balloons for
>> +     compound literal syntax, e.g., (struct foo){ .member = value };
>> +     our hope is that no platforms we care about have trouble using
>> +     them, and officially adopt its wider use in mid 2026.  Do not add
>> +     more use of the syntax until that happens.
>> +
>>      New C99 features that we cannot use yet:
>>        . %z and %zu as a printf() argument for a size_t (the %z
>> being for