[swift-evolution] What about garbage collection?

[Goffredo Marocchi]

On a similar note though, I think if we are taking the point of view that simplifying the memory model and making it safer is worth lots of complexity trade offs I would go all the way in that direction and look real hard at the outcome of MS's project Midori rather than stopping at a GC, but it is kind of getting very off topic so I will cut this short.

Sent from my iPhone

> On 8 Feb 2016, at 21:04, Frank Ecsedy via swift-evolution <swift-evolution at swift.org> wrote:
> 
> In fact, Java is looking to introduce value types and will have to wrestle with how to do it in a pure GC environment. For Swift a GC is lots of pain for minimal gain or even a net loss.
> 
>> On Monday, February 8, 2016, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> on Mon Feb 08 2016, Félix Cloutier <swift-evolution at swift.org> wrote:
>> 
>> > Has there been a garbage collection thread so far? I understand that
>> > reference counting vs. garbage collection can be a heated debate, but
>> > it might be relevant to have it.
>> >
>> > It seems to me that the two principal upsides of reference counting
>> > are that destruction is (essentially) deterministic and performance is
>> > more easily predicted. However, it comes with many downsides:
>> >
>> > object references are expensive to update
>> > object references cannot be atomically updated
>> > heap fragmentation
>> > the closure capture syntax uses up an unreasonable amount of mindshare
>> > just because of [weak self]
>> >
>> > Since Swift doesn't expose memory management operations outside of
>> > `autoreleasepool`, it seems to me that you could just drop in a
>> > garbage collector instead of reference counting and it would work (for
>> > most purposes).
>> >
>> > Has a GC been considered at all?
>> 
>> Yes.  Among other problems, you can't do copy-on-write efficiently with
>> a GC, because you can't detect a unique reference.  And without
>> efficient copy-on-write, most interesting value types (Array) are out
>> the window.
>> 
>> --
>> -Dave
>> 
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