[mistercow]

> (I believe modern Objective-C is compiler supported refcounting though so this doesn't really apply here)

Yeah, I don't think they ever supported GC in iOS. Now that you mention it, it's probably not a coincidence that it was added to the Mac shortly after the entire product line had switched to 64-bit. You could still do it in 32-bit, but I doubt they were expecting many developers to start writing new 32-bit apps at that point.

What does use a conservative garbage collector on iOS, however, is Safari's JS engine. But I assume that the conservative scan is only used on the stack (that's what FF does), since it would be kind of silly to do a conservative scan of the heap for a language that doesn't support pointers. So it doesn't seem likely under normal circumstances that you'd have many false hits even with 32-bits.