Disadvantages of ARC

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On Thursday, 6 February 2014 at 13:23:14 UTC, Sönke Ludwig wrote:
> Am 06.02.2014 12:37, schrieb Max Klyga:
>> Anti-GC crowd tries to promote ARC as an deterministic 
>> alternative for
>> memory management.
>> I noticed that people promoting ARC do not provide any 
>> disadvantages for
>> proposed approach.
>>
>> The thing is in gamedev and other soft-realitime software 
>> background
>> only a handfull types of resources are really managed by RC 
>> and memory
>> usage patterns are VERY specific to their domain (mostly linear
>> allocation/deallocation and objects with non deterministic 
>> lifetime are
>> preallocated in pools).
>>
>> Trying to use RC as a general method of memory management 
>> leads to some
>> problems.
>> A pretty detailed view by John Harrop (He is somewhat known 
>> for trolling
>> in PL community, but nonetheless knows what he is talking 
>> about) -
>> http://www.quora.com/Computer-Programming/How-do-reference-counting-and-garbage-collection-compare/answer/Jon-Harrop-1?srid=3Gvg&share=1#
>>
>>
>> So RC could also introduce unpredictable pause times at 
>> undesired places.
>>
>> This is also confirmed by research from HP -
>> http://www.hpl.hp.com/personal/Hans_Boehm/popl04/refcnt.pdf
>>
>> My point is that we should not ruin the language ease of use. 
>> We do need
>> to deal with Phobos internal allocations, but we should not 
>> switch to
>> ARC as a default memory management scheme. In practice people 
>> promoting
>> ARC will probably not use phobos anyway. Currently its just an 
>> excuse to
>> not use D.
>>
>> Look at c++ and STL, etc. People will roll their own solutions 
>> no matter
>> what you try.
>>
>
> Full ACK! Reference counting should be well supported, but it 
> shouldn't be the default scheme or built-in at a low level. 
> From my personal experience it would be ideal to be able to 
> customize certain types to be reference counted (allowing the 
> user full flexibility implementing the actual reference 
> counting and without ruling out weak references!), but have 
> them accessible using the same syntax and type conversion 
> semantics as normal references.

I think the best way forward would be to look at the places in D 
where allocations happen, and then figure out how we can 
optionally allow reference counting in these situations. Andrei 
just made a thread on this yesterday in regard to slices, which I 
think are the most promising for a RC solution.