Michel Fortin wrote: Le 26-juin-2013 à 19:48, Walter Bright a écrit :
> D (like C and C++) loves to manipulate pointers. Having to call a function every time this is done would be a disaster. It means that people would be motivated to drop down to C to do the fast code, and we might as well throw in the towel.
But at the same time, having a GC that stops the world at irregular interval is worse for certain kind of things, games notably. It's been stated often on the forum that game developers prefer increasing the overhead if it prevents those hiccups. Making everything in D reference-counted would undoubtedly increase the general overhead, but it'd allow game developers to leverage the whole language and its libraries instead of restricting themselves to a custom subset of the class hierarchy derived from a reference counted class.
And about pointer manipulation: for cases where you know for certain that the pointer still points to the same memory block before and after the assignment (when you call popFront on an array for instance), you have no reference count to update and can elide the call.
The downside of optional support for language-wide reference counting is that it requires two incompatible codegen (or rather one incompatible with RC). We could have only one if it's the one that calls the retain/release functions on pointer assignment, with those functions replaced with empty stubs in druntime when reference counting is disabled, but some overhead would remain for the function call.
I'm not claiming this is the right solution. It's just an idea I wanted to mention as an aside because it has some common points. It is however a mostly separate matter from your initial goal of supporting custom reference counting schemes for some object hierarchies. I decided to write about it mostly because you talked about reimplementing arrays using classes and that got me thinking. But perhaps I shouldn't have mentioned it because it seems to be side-tracking the discussion.
