[swift-evolution] [swift-evolution-announce] [Review] SE-0159: Fix Private Access Levels

[David Hart]

> On 23 Mar 2017, at 16:49, Drew Crawford <drew at sealedabstract.com> wrote:
> 
> 
> 
> 
>> On March 23, 2017 at 2:22:20 AM, David Hart (david at hartbit.com) wrote:
>> 
>> > We will get static linking at some point in the near future.
> 
> Static linking does not fix this issue. Just change "framework" to ".a".
> 
I'm curious to hear what issue your client had with you using many frameworks that static linking doesn't solve.

>> > If we wait until we get submodules, we won't be able to revisit. This is probably our last chance to "remove" a feature. Submodules can always add features down the way.
> 
> Maybe submodules will solve this issue, maybe not.  But submodules are *much* more complex than scoped access:
> 
> * Performance.  This is hot code we compile with WMO.  Moving it into a submodule could reduce visibility for optimization in a way that causes a performance regression.  In particular, we know that specialization of T is a performance requirement, it isn't clear whether that would be preserved.  Does WMO provide the same visibility across submodules?  Nobody knows.
> 
I don't see why submodules could not profit from WMO: the module is still compiled all together. Submodules are simply a scoping/hiding mechanism.
> * Namespacing.  It's possible that one program may ship 3-4 versions of this code because each dependency has a slightly different version under our current samizdat process.  It is not clear whether submodules would avoid the "duplicate symbols" issue from C/ObjC.  Xiaodi seems quite concerned about a related "duplicate functions" problem involved with private today, doubling down on that is not a good idea.
> 
That looks like a very corner case. I haven't yet found myself in the case where I needed multiple versions of a code base in a same product (binary, framework, application)
> * It is not clear whether submodules are from an objectcode point of view merged into the parent library or kept as individual libraries
> 
It would be very strange to me if they were independent libraries: what would different them from modules then? No other language I've used works that way.
> * It is not clear from a .swiftmodule point of view whether submodules are merged into the parent module or distributed as .swiftmodules / .swiftdocs
> 
> * Not clear how much ABI impact there is from submodules at a time when we are supposed to be trying to stabilize it
> 
> I would love to believe that a proposal on submodules will come through having solutions to all these issues and many more, then we will implement it and all sing kumbayah.  But we are a long distance from that, and it may never happen at all, certainly we cannot evaluate proposals that haven't been written.  Meanwhile we have a solution in the hand.
> 
But at the same time, we can't write and review proposals with no regard for future proposals coming down the road or we end up with a clunky language.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20170323/7230c621/attachment.html>