Memory management design

[Michel Fortin]

On 2013-07-10 08:00:42 +0000, Manu <turkeyman at gmail.com> said:

> I'd push for an ARC implementation. I've become convinced that's what I
> actually want, and that GC will never completely satisfy my requirements.

There's two ways to implement ARC. You can implement it instead of the 
GC, but things with cycles in them will leak. You can implement it as a 
supplement to the GC, where the GC is used to collect cycles which ARC 
cannot release. Or you can implement it only for a subset of the 
language by having a base reference-counted class and things derived 
from it are reference counted.

The two first ideas, which implement ARC globally, would have to call a 
function at each and every pointer assignment. Implementing this would 
require a different codegen from standard D, and libraries compiled 
with and without those calls on pointer assignment would be 
incompatible with each other.

On the other end, having a reference counted base class is of more 
limited utility because you can't reuse D code that rely on the GC if 
your requirement does not allow the GC to run when it needs too. But it 
does not create codegen fragmentation.

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