Question

I am using Instruments to find memory leaks in my app.
When a object alloc, a blue block(line) display in Instrument, like this:

Screenshot of Instruments's timeline, showing the Allocations graph http://naituw.com/temp/instruments.png

When the object have been release, the blue line will disappear.

But when I make some operation in my application, some blue block left there, doesn’t disappear, How can I know what those block actually is in the memory? Thanks!

Answer 1

Select the instrument and look in the list in the lower half of the window. It will show a table or outline (depending on the instrument) listing what the instrument recorded.

For the Allocations instrument, it lists things your application has allocated. Depending on the view settings, they may be objects that are still alive or all objects, even those that you have freed.

For the Leaks instrument, it lists things your application has allocated and leaked (i.e., no longer has any reference to). Note that you might still be wasting ever-increasing amounts of memory on things you will never use, not because you don’t have a reference to it but because it’s in a write-only cache (you stash it but never look it up) or similar situation. Bill Bumgarner calls this “abandoned memory”.

With either instrument, you can click on ➲ buttons within the list to drill deeper down into it, to see the list of allocations of a given type (e.g., all NSImages) or everything that happened to a single object, from birth to death. The latter is extremely useful for hunting down both leaks and over-release crashes, and is the reason why Instruments’s Zombies template is so much better than NSZombieEnabled.