Reference counting worth a try
by Leandro Lucarella on 2008- 08- 18 23:30 (updated on 2008- 08- 19 02:19)- with 0 comment(s)
Even when I said that reference counting (RC) will be hard in D, I think it worth a try because it's a really easy way to get incremental garbage collection; the collector activity is interleaved with the mutator. And besides it could be hard to add support to the compiler, it's doable by manually incrementing and decrementing the reference counters to evaluate it.
One of the biggest features of RC is its capability to identify garbage cells as soon as they become garbage (let cycles outside that statement =). The killer use for this is finalization support. Unfortunately this feature kills a lot of possible optimizations. On the other hand, D doesn't need finalization support very hard (with the scope statement and other possible RAII D techniques, I think nobody is missing it), so, lucky us, we can drop that feature and think about some optimizations.
RC can help too to all the fuzz about concurrency and sharing in D2 (it's trivial to know when an object is unshared), but that's a different story.
Note
By the way, I don't think RC can make it on his own (yes, because of cycles), but I think it can help a lot to make collection incremental, leaving just a very small ammount of work to a tracing collector.