D on next-gen consoles and for game development

[Paulo Pinto]

Am 25.05.2013 07:52, schrieb Manu:
> On 25 May 2013 15:29, deadalnix <deadalnix at gmail.com
> <mailto:deadalnix at gmail.com>> wrote:
>
>     On Saturday, 25 May 2013 at 05:18:12 UTC, Manu wrote:
>
>         On 25 May 2013 15:00, deadalnix <deadalnix at gmail.com
>         <mailto:deadalnix at gmail.com>> wrote:
>
>             On Saturday, 25 May 2013 at 01:56:42 UTC, Manu wrote:
>
>                 Understand, I have no virtual-memory manager, it won't
>                 page, it's not a
>                 performance problem, it will just crash if I
>                 mis-calculate this value.
>
>
>             So the GC is kind of out.
>
>
>         Yeah, I'm wondering if that's just a basic truth for embedded.
>         Can D implement a ref-counting GC? That would probably still be
>         okay, since
>         collection is immediate.
>
>
>     This is technically possible, but you said you make few allocations.
>     So with the tax on pointer write or the reference counting, you'll
>     pay a lot to collect very few garbages. I'm not sure the tradeoff is
>     worthwhile.
>
>
> But it would be deterministic, and if the allocations are few, the cost
> should be negligible.
>
>
>     Paradoxically, when you create few garbage, GC are really goos as
>     they don't need to trigger often. But if you need to add a tax on
>     each reference write/copy, you'll probably pay more tax than you get
>     out of it.
>
>
> They're still non-deterministic though. And unless (even if?) they're
> precise, they might leak.
>
> What does ObjC do? It seems to work okay on embedded hardware (although
> not particularly memory-constrained hardware).
> Didn't ObjC recently reject GC in favour of refcounting?

Yes, but is was mainly for not being able to have a stable working GC 
able to cope with the Objective-C code available in the wild. It had 
quite a few issues.

Objective-C reference counting requires compiler and runtime support.

Basically it is based in how Cocoa does reference counting, but instead 
of requiring the developers to manually write the [retain], [release] 
and [autorelease] messages, the compiler is able to infer them based on
Cocoa memory access patterns.

Additionally it makes use of dataflow analysis to remove superfluous use 
of those calls.

There is a WWDC talk on iTunes where they explain that. I can look for 
it if there is interest.

Microsoft did the same thing with their C++/CX language extensions and 
COM for WinRT.

--
Paulo