[llvm-dev] Improve JIT C API

[James Y Knight via llvm-dev]

On Sep 8, 2015, at 12:55 AM, Eric Christopher via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> 
> On Mon, Sep 7, 2015 at 5:37 PM Lang Hames <lhames at gmail.com <mailto:lhames at gmail.com>> wrote:
> Hi Jauhien,
> 
> A few people have requested a C API for ORC. I don't think ORC's ready for a stable C API, but I'm not opposed to providing C bindings that will probably be reasonably stable in practice (though with no guarantees). I've actually already knocked up some trivial prototype bindings for Hayden Livingston that could serve as a base (see attached).
> 
> The next question is where unstable bindings should live. Juergen, Eric, anyone else who wants to weigh in: I looked back over the C API thread, but I don't think we settled on a home for this kind of thing. Any thoughts? I could see either introducing a new include directory (something along the lines of include/llvm/llvm-c-bindings) or a new c-bindings project on llvm.org <http://llvm.org/>. The former would put all LLVM developers on the hook for maintaining the bindings, the latter would leave maintenance to users of the bindings project, and any volunteers. I prefer the second option: I don't think core developers should be on the hook for maintaining unstable bindings - that kind of special treatment should be reserved for the stable API.
> 
> 
> We hadn't figured out a location. I was the one that wanted to move stable to a new directory and Jim wanted to move unstable. I think either will work ultimately, just a matter of personal preference in the "when do we count restart".
> 
> That said, as long as you put a comment at the top saying that the ORC bindings are unstable and put them in a new file I'm not opposed to just putting them in llvm-c for now. I also don't think I'm going to win the argument of "stable moves" so if you'd like to make a new unstable directory I'm perfectly happy with that direction too.
> 
> Thoughts?

+1 to putting it in llvm-c for now (but also for good).

I really think the existing LLVM-C APIs should all be considered "reasonably stable in practice", not "absolutely 100% stable forever". "Reasonably stable in practice" means to me: if you need to remove a function, then, ok, do that. But make a reasonable effort to avoid doing so first, for users' sake. And don't change the ABI of existing functions.

And thus, if ORC is at that level (probably is?), I think it should just go in there with all the rest of them.

BTW, have a patch: http://reviews.llvm.org/D12685 saying that in more words.
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