[swift-evolution] A case for postponing ABI stability

[Rick Mann]

Thanks for that, that's helpful.

My concern, of course, is the obvious one: that we'll have to compromise on future functionality in order to not break ABI compatibility, or we'll have a painful transition when we do break it. While today it's suboptimal to ship copies of the runtime with each application, it's a working solution.

I'd really like to make sure Swift can be fully introspective (soon), but I don't know how easy it will be to add that after the ABI is locked down. Maybe I'm just being alarmist. I'd also like to see the ability to replace code at run time.

If all that is already accommodated by the current ABI, then I'm satisfied. But it seems like there's some concern about this, and I worry that locking down the ABI too early will make those additions MUCH harder in the future.

Thanks!

> On Jan 25, 2017, at 15:09 , Michael Ilseman <milseman at apple.com> wrote:
> 
> As described in e.g. https://github.com/apple/swift/blob/master/docs/ABIStabilityManifesto.md#what-does-abi-stability-enable, it primarily enables OSes to ship with a copy of the standard library and runtime, rather than every app having to bundle their own copy. It’s also a crucial piece of supporting 3rd party frameworks. There are also more subtle benefits such as the de-coupling of developer tools that work with Swift binaries (e.g. debuggers and profilers). Some of the tasks towards stability are performance improvements we want to do anyways.
> 
> 
> 
>> On Jan 25, 2017, at 1:36 PM, Rick Mann via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> I'm also late to the thread (and the ABI stability discussion in general). Is there a reference online that describes the reason for desiring ABI stability? I mean, I get, generally, why we need it. But I'd like to see the arguments for why we need it *now*, before certain other things are in place. Not saying the reasons for the urgency aren't valid, I just don't know what they are.
>> 
>> Thanks!
>> 
>>> On Jan 25, 2017, at 08:44 , Freak Show via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> This is both great to hear (ivar introspection available) and a little disappointing (method level not).  Basically, I would hope for at least enough to allow implementation of KVC - which would require the ability to find and invoke methods by name.
>>> 
>>> 
>>> 
>>>> On Jan 24, 2017, at 14:16, Joe Groff <jgroff at apple.com> wrote:
>>>> 
>>>> a lot of the information you'd need for many dynamic features is already there, and planned to be stabilized as part of the ABI. We already emit reflection data that describes the physical layouts of types, and once those formats are stabilized, building a library that interprets the metadata is additive (and could conceivably be done by a third party independent of the standard library). There may not be metadata for individual methods yet
>>> 
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>> 
>> 
>> -- 
>> Rick Mann
>> rmann at latencyzero.com
>> 
>> 
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-- 
Rick Mann
rmann at latencyzero.com