[llvm-dev] An Update on the C API

Sean Silva via llvm-dev llvm-dev at lists.llvm.org
Thu Nov 19 17:55:25 PST 2015

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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