[LLVMdev] [RFC] Developer Policy for LLVM C API

[Eric Christopher]

I think the idea of having a (hopefully not too) fluid C API that can
encompass everything people want to be able to do in the language of their
choice and calls into LLVM to do work sounds like a great idea. I think it
would be useful to expand the number of people who are able to do research
and development with LLVM without having to reinvent LLVM. That said, this
is directly at odds with our desire to have a stable C API that can be
supported long term (as you said at the end of the email). I.e. where do we
draw the line on what can or should be added to the C API? What if the
people that want the functionality are willing to deal with it being
(occasionally) unstable?

I don't agree with you that no one will take the time to design a well
thought out C API. We've managed to get a lot of real world experience
lately at both how these things will be used, and how we'll maintain such a
thing. I think Juergen and others are a good group to come up with an
answer to our engineering challenge.

-eric

On Thu, Jul 30, 2015 at 11:54 AM Reid Kleckner <rnk at google.com> wrote:

> +1, I agree with keeping the existing C API stable, and requiring one
> release of deprecation with an alternative in place to remove something
> from it.
>
> Nobody is going to take the time to design a well-thought out C API that
> is powerful enough for frontend IRGen and is forward compatible with future
> versions of LLVM. That's an unsolved problem. We should stick with what we
> have.
>
> The only thing we can do to keep LLVM flexible is to limit the set of new
> things we expose over the C API boundary, which I'm totally in favor of.
>
> On Fri, Jul 17, 2015 at 12:36 PM, Juergen Ributzka <juergen at apple.com>
> wrote:
>
>> Hi @ll,
>>
>> a few of us had recently a discussion about how to manage the C API and
>> possible policies regarding addition, maintenance, deprecation, and removal
>> of API.
>>
>> Even thought there is a strong agreement in the community that we
>> shouldn't break released C API and should be backwards compatible, there
>> doesn’t seem to be a developer policy that backs that up. This is something
>> we should fix.
>>
>> I was wondering what the interested parties think of the current approach
>> and what could/should we improve to make the use and maintenance of the C
>> API easier for users and the developers alike.
>>
>> I was hoping we could also introduce a process that allows the removal of
>> an API after it has been deprecated for a whole release and the release
>> notes stated that it will be removed.
>>
>> Thoughts? Comments?
>>
>> Cheers,
>> Juergen
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