The [core of OS X](http://www.osxbook.com/book/bonus/ancient/whatismacosx/arch_xnu.html) **is not garbage collected**. IOKit's [libkern C++ Runtime](https://developer.apple.com/library/mac/documentation/DeviceDrivers/Conceptual/WritingDeviceDriver/CPluPlusRuntime/CPlusPlusRuntime.html#//apple_ref/doc/uid/TP30000695-BAJIBFDE) requires developers to manage their own memory.

Garbage collection exists at the user or application layer. Even at this layer, garbage collection only helps if the application has released all claims to the memory. A circular dependancy can defeat garbage collection. Garbage collection itself is an evolving area of research and [difficult to get right](http://xkcd.com/1425/).

Bugs within OS X will be leaking memory. Given the size of the code base, this is almost certain.

Please [report reproducible bugs directly to Apple](https://bugreport.apple.com/). Every bug report helps and maybe your example will be the one that helps Apple's engineers pin down the cause.