D/Objective-C 64bit

[Michel Fortin]

On 2014-03-12 08:06:47 +0000, "w0rp" <devw0rp at gmail.com> said:

> This is really awesome work. If you combined ARM support with Objective 
> C support, it would mean you could write iOS programs in D without much 
> frustration, and that would be a huge step forward. Objective C has a 
> good runtime, but lacks templates and CTFE. Using CTFE for an iOS 
> program could be very cool.
> 
> How do you plan to handle automatic reference counting? I imagine 
> that's a hard part. When I was writing Objective C I remember having to 
> write bridged casts so I could manually extend or limit object 
> lifetime, but I never handled it from within a C library.

Well, there's three ways.

(a) The first one is to implement ARC for Objective-C objects, and to 
automatically add/remove roots to member variables when 
constructing/destroying Objective-C objects that were defined in D so 
the GC can those pointers.

(b) The second one is to not implement ARC and implement something in 
the GC so it can track Objective-C objects: retain them on first sight, 
release them once no longer connected to a root.

(c) The third one is to implement ARC as an alternative memory 
management scheme for D and bolt Objective-C object support on top of 
it.

I'd tend to go for (a) at first, as it's the simplest thing that can be 
done. But I fear always adding/removing roots will impact performance 
in a negative way. There's also the issue in (a) and (b) that if the 
last reference to an object is released from the GC thread the 
Objective-C object's destructor will be called in a different thread 
than what is expected which might cause some bugs. So we might want to 
implement (c) later on to have something more solid and deterministic.

-- 
Michel Fortin
michel.fortin at michelf.ca
http://michelf.ca