The core of OS X is not garbage collected; IOKit's libkern C++ Runtime requires developers to manage their own memory.

Mac Memory Management

From How does memory management work in Mac OS X?

Apple documents the lowest levels of the Mach Kernel and the virtual memory subsystem fairly well on the web as part of it's developer documentation.

• Kernel Programming Guide: Memory and Virtual Memory

Since that kernel was developed by Carnegie Mellon University, you can find dozens of papers describing it quite easily.

Other Sources

• Wikipedia discusses Mac OS memory management.

• Apple's support note: Use Activity Monitor to read system memory and determine how much RAM is being used

Garbage Collection

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.

Report Bugs and Memory Leaks

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. Every bug report helps and maybe your example will be the one that helps Apple's engineers pin down the cause.

Please try this. Click on Mail > Preferences > Viewing There will be a dropdown for list preview. Select a choice other than None. That will give summary information about the email message you have selected. Make sure you select an email. The actual email message should appear to the right of the summary. If it does not, you'll probably need to move your cursor as far to the right of the screen as you can go. Push down your mouse or track pad and move the cursor to the left. You should see the email that is selected.