<div dir="ltr"><br><br><div class="gmail_quote"><div dir="ltr">On Thu, Jul 30, 2015 at 3:36 PM Philip Reames <<a href="mailto:listmail@philipreames.com">listmail@philipreames.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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It's sounds like we've reached two rough conclusions:<br>
1) We need both a stable and a non-stable fully featured C API.
It's a somewhat open question whether both or either should be part
of the main tree. <br></div></blockquote><div><br></div><div>I'm fine with the stable API being in the main tree. I proposed moving it out originally so that it could get some work before moving it in. I'm reasonably confident that we can get something working in tree for a stable API by the next release though.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
2) Everyone seemed okay with the proposed deprecation policy for the
stable API.<br>
<br></div></blockquote><div><br></div><div>Yes.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
Given this, I would propose we designate the existing C API as the
"hopefully stable, but subject to future clean up per policy..."
Update </div></blockquote><div><br></div><div>This is where we disagree. I've tried to lay out a design that I think would be good for a stable API and the current one does not meet any guidelines there. It's too much a thin wrapper on top of the existing C++ API. There's no clear delineation for when/how/whether we extend it. It's already easy to subtly break the existing one.</div><div><br></div><div>My proposal here is simply thus:</div><div><br></div><div>We deprecate the existing API as "moving to unstable". For the next release cycle, as a new C API comes into existence, we continue our best effort toward keeping the existing API as stable as possible ("best effort") just like we always have. At the next release we flip the switch that says "this is now not stable, please use X". In the mean time we can either a) move a bindings level C API into a separate directory starting with the existing wrapped C++ API that we have as part of the C API, or b) expand in the current directory and copy a set of APIs off to another directory. How to do this with minimal churn in external projects is important - this is why I'm inclined to say that the bindings API reside in the current C API directory, but others are more hesitant, I'm just not sure in their mind how the final transition from "best effort stable" to "stable".</div><div><br></div><div>-eric</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">the documentation to note that LLVM does not currently have a
fully featured C API. Update the docs to reflect the deprecation
policy for the existing C API. <br>
<br>
We can then start discussing how we should create the fully featured
API. I'd lean towards a tool like Swig, but we could also do it
purely on demand. For example, I could add some shims for the
experimental GC support without committing to supporting the current
APIs long term. <br></div><div bgcolor="#FFFFFF" text="#000000">
<br>
Philip</div><div bgcolor="#FFFFFF" text="#000000"><br>
<br>
<div>On 07/30/2015 01:47 PM, Reid Kleckner
wrote:<br>
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<div class="gmail_quote">On Thu, Jul 30, 2015 at 1:04 PM, Eric
Christopher <span dir="ltr"><<a href="mailto:echristo@gmail.com" target="_blank">echristo@gmail.com</a>></span>
wrote:<br>
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<div>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?</div>
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<div>Yeah, splitting the concerns of API completeness and
API stability seems like a good idea. Right now we have
clients like llgo that want to generate new debug info,
and are perfectly happy to keep up to date with changes.
They need a complete API, not a stable API, and our
insistence on a stable C API has actually gotten in the
way here.</div>
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<div>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.</div>
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<div>Sure, if people are planning to design a stable API
that leave LLVM with more flexibility, then I'm all in
favor of switching over to it. So far I haven't heard any
new suggestions. I think any such design would probably be
write-only, and revolve around sharing the bitcode
auto-upgrade logic.</div>
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