How should I interpret the "all allocations" data in the Leaks Instrument?

Question

I have written an app and was testing it for memory leaks when I noticed that the "all allocations" category in the leaks simulator keeps increasing its size whenever I open and close a sub-view.

I intially thought it was a memory leak, but it does not show up as a leak in the leaks tab.

Is this normal?

Answer 1

It depends which column of the table you are looking at.

The 'Overall' and 'Overall Bytes' figures will always go up, since they are a running count of allocations made with no account of deallocations.

However, the 'Live Bytes' and '# Living' figures should go up when an object or block of memory has been allocated, but should go down when they are deallocated.

Repeatedly opening and closing a sub-view should (subject to image or data caching) hover around a fixed number of live bytes and living objects / memory blocks.

Instruments sometimes gets a bit confused, however, as you can see from the screenshot. The whole '# Transitory' column is showing '0', which is obviously incorrect. A transitory object is just one that has been allocated and subsequently deallocated, i.e. it's a non-living object.

(# Living + # Transitory == # Overall)

Whenever Instruments gives me that column of zeros, I quit the current run and start a new one.

As for the Leaks Instrument, it will only show those objects or memory blocks that no longer have any pointers pointing to them. If a program continually allocates more and more objects / memory blocks but retains pointers to them, the Leaks Instrument won't show them.

Answer 2

That would make sense would it not? Every time you do something in the app, something is probably allocated such as your different subviews. Therefore total allocations will increase.It's just a record of the total allocations.