Hacker News Reader

Comment by sanderjd | Hacker News Reader

> You implement some kind of reference counting?

Yep! Or, ideally, you use one of the good reference counting libraries that your language almost certainly ships with if it is one which encourages RAII.

View on HN

Reference counting is just one form of garbage collection, the other main alternative is a collecting garbage collector. And comparisons showed - I know that they tried both for .NET - that a collecting GC outperforms a reference counting GC. Yes, you will have to take a performance hit when you perform garbage collection in cases where it would not be necessary but the convince of not having to care far outweighs this because program correctness is important and development time expensive, computing power is cheap and does not matter. At least in my field, mainly business applications.

Well, reference counting is definitely a way to collect garbage, but when people say X language used a reference counting GC versus a collecting GC, they typically mean that X language was using that GC for all objects. I'm guessing that the .NET experiment you're thinking of used the terminology in that way, and if so, I don't think it's particularly surprising that reference counting was slower. But using a reference counting library only in cases where you find that you need multiple references to a single object is a very different animal. Most programs don't actually need much shared data, even without any design contortions.

Of course, you are right, I did not want to imply that we should call C++ a garbage collecting language just because it has shared_ptr. And you are right that you can achieve more optimal code if you can use you knowledge to decide when reference counting is necessary and when not. But there is just an enormous spectrum of cases where the convenience of a garbage collector - which gives you less (but not zero) opportunities for memory leaks and speeds up development - far outweighs the performance hit. And the performance hit is really not large, modern garbage collectors are highly tuned pieces of software. Obviously you probably don't want a GC run when you are in the middle of some timing critical driver code, but I never wanted to imply a black/white world where garbage collectors are the silver bullet. But the article is definitely wrong - garbage collection is not wrong (in all scenarios).

> But there is just an enormous spectrum of cases where the convenience of a garbage collector - which gives you less (but not zero) opportunities for memory leaks and speeds up development

I think the article is actually more of an argument against that line of reasoning than an argument about performance. Its main proposition is that properly used RAII gives you less opportunities for resource leaks of all sorts, and is very easy to do. I agree with you that it isn't wrong in all scenarios (I mostly program in Ruby and Javascript for goodness sake!), but I think a lot of people are unaware of some of the advances in patterns, libraries, and compilers that make it much easier to write software that doesn't need a GC.

Reply on news.ycombinator.com