[llvm-dev] An Update on the C API

[Eric Christopher via llvm-dev]

I've done this now btw. A few additional commits on some non-ascii quotes
and one clarification.

Feel free to follow up with any different or clarified text.

Thanks everyone!

-eric

On Thu, Nov 19, 2015 at 5:57 PM Eric Christopher <echristo at gmail.com> wrote:

> "Documentation:
>
> We’re going to document this policy in the developer documentation. In
> addition, any changes to the C API will require documentation in the
> release notes so that it’s clear to external users who do not follow the
> project how the C API is changing and evolving."
>
> So, yes?
>
> -eric
>
> On Thu, Nov 19, 2015 at 5:55 PM Sean Silva <chisophugis at gmail.com> wrote:
>
>> Are you going to propagate this info into
>> http://llvm.org/docs/DeveloperPolicy.html ?
>>
>> On Thu, Nov 19, 2015 at 1:56 PM, Eric Christopher via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>>
>>> Hi All,
>>>
>>> I wanted to send a follow-up mail to the C API discussion/BoF that we
>>> had at the latest developer meeting and nicely hosted by Justin and Juergen.
>>>
>>> We were able to reach consensus on a number of questions/concerns about
>>> the C API so I’m going to go ahead and list them for posterity and for any
>>> further discussion here:
>>>
>>> Stability Guarantees:
>>>
>>> The C API is, in general, a “best effort” for stability. This means that
>>> we’ll make every attempt to keep the C API stable, but that stability will
>>> be limited by the abstractness of the interface and the stability of the
>>> C++ API that it wraps. In practice, this means that things like “create
>>> debug info” or “create this type of instruction” is likely to be less
>>> stable than “take this IR file and JIT it for my current machine”.
>>> Release stability:
>>> We won’t break the C API on the release branch with patches that go on
>>> that branch - in general.
>>> Exception: If we fix an unintentional C API break that will keep us
>>> consistent with both the previous and next release.
>>>
>>> Including new things into the API:
>>>
>>> We’re going to adopt a policy of “if a particular LLVM subcomponent has
>>> a C API already included, then expanding that API is acceptable”, but we’re
>>> also going to institute a better policy of “please test the API that you’ve
>>> just expanded”. Hopefully this will get the C API better tested as time
>>> goes on to remove accidental breakage so that any time we break the C API
>>> we know about it.
>>>
>>> Adding C API for subcomponents that don’t currently have one is also
>>> fine, and the details of how best to do that should be discussed on the
>>> mailing list as they come up.
>>>
>>> Documentation:
>>>
>>> We’re going to document this policy in the developer documentation. In
>>> addition, any changes to the C API will require documentation in the
>>> release notes so that it’s clear to external users who do not follow the
>>> project how the C API is changing and evolving.
>>>
>>> What we expect this means in practice is that APIs like libLTO and other
>>> APIs based on reading IR are going to remain highly stable and that more
>>> wrapper like APIs (IR creation, etc) are going to both be added and change
>>> as the underlying IR changes.
>>>
>>> Please feel free to follow up to this thread with any concerns.
>>>
>>> Thanks!
>>>
>>> -eric (with Justin and Juergen)
>>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
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