Do I need to Start the Garbage Collector?

Running through the Core Data Utility Tutorial, and it says that I need to turn on garbage collection in the build settings, and add the function call

Code:

objc_startCollectorThread();

in order to "start the garbage collector." Now in all the applications I've written so far, I turned on the garbage collector in the build settings, but I never heard of this function call before. Does that mean that the garbage collector wasn't working in my previous apps, or is this requirement just for command line tools?