D on next-gen consoles and for game development

[Paulo Pinto]

On Wednesday, 29 May 2013 at 07:18:49 UTC, Rainer Schuetze wrote:
>
>
> On 29.05.2013 02:46, Steven Schveighoffer wrote:
>> On Tue, 28 May 2013 20:40:03 -0400, Manu <turkeyman at gmail.com> 
>> wrote:
>>
>>
>>> ObjC and WinRT are both used successfully on embedded 
>>> hardware, I'm
>>> really
>>> wondering if this is the way to go for embedded in D.
>>> V8 uses an incremental collector (somehow?), which I've been 
>>> saying is
>>> basically mandatory for embedded/realtime use. Apparently 
>>> Google agree.
>>> Clearly others have already had this quarrel, their 
>>> resolutions are worth
>>> consideration.
>>
>> An interesting thing to note, Apple tried garbage collection 
>> with Obj-C,
>> but only on MacOS, and it's now been deprecated since automatic
>> reference counting was introduced [1].  It never was on iOS.
>>
>> So that is a telling omission I think.
>>
>> -Steve
>>
>> [1] 
>> https://en.wikipedia.org/wiki/Objective-C#Garbage_collection
>
> Please note that you have to deal with circular references 
> manually in Objective-C, introducing two types of pointers, 
> strong and weak. I don't think this is optimal. If you want to 
> deal with circular references automatically you again need some 
> other kind of other garbage collection running.
>
> A problem with the naive approach of atomic reference counting 
> a counter inside the object (as usually done in COM interfaces, 
> I don't know how it is done in Objective-C) is that it is not 
> thread-safe to modify a pointer without locking (or a CAS2 
> operation that you don't have on popular processors). You can 
> avoid that using deferred reference counting (logging pointer 
> changes to some thread local buffer), but that introduces back 
> a garbage collection step with possibly massive destruction. 
> This step might be done concurrently, but that adds another 
> layer of complexity to finding circles.
>
> Another issue might be that incrementing a reference of an 
> object when taking an interior pointer (like you do when using 
> slices) can be pretty expensive because you usually have to 
> find the base of the object to access the counter.
>
> I won't dismiss RC garbage collection as impossible, but doing 
> it efficiently and concurrently is not so easy.

There is a nice document where it is described alongside all 
restrictions,

https://developer.apple.com/library/mac/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html#//apple_ref/doc/uid/TP40011226