Have an app that's an iOS app with a Messages extension app. They share a significant amount of code related to calculating & editing the dimensions of some specialized objects and then using that to create paths for drawing.
The app was running perfectly. A build of the Messages app crashed with EXC_BAD_ACCESS code=2, seemingly within the code that's shared. No luck debugging it, as the location of the crash seemed to bounce around as I added log statements and refactored the code.
So I focused on the main app. First try was turning on Address Sanitizer, and that created the crashes discussed below. Then I edited the scheme to look for Zombies, and none were identified, including in Instruments. No memory leaks or other obvious allocation errors via Instruments. I edited the scheme to turn on Malloc Scribble, Malloc Guard Edges, and Guard Malloc, and the app ran fine with no crash or console log message.
So back to Address Sanitizer, which is the only option that caused the main app to crash, and it crashed in the same area as the Messages app. I figured if I solved one, I might solve both, and the app might be easier to debug without the complication of being an extension.
Every link I searched and read seemed to say that these Xcode diagnostics will (or should) identify the offending code, and in years of writing Swift, that's the typical case. This one has me stumped.
The main view controller is a UICollectionViewController, and the crash occurs at the very first collectionView(:cellForItemAt) call. There's nothing unusual about the other delegate calls, afaik, with normal (and accurate) counts and sizes. (And again, this is just with Address Sanitizer.) After getting the reusable cell, I call getObjectEffects with some default values (the app is more complex, but it crashed also on this ultra-simple hard-coded values case too, so I'm keeping the debugging as simple as possible), and the EXC_BAD_ACCESS is identified for the func definition of that function.
That's what stumps me. It's not identifying code where there's an assignment or allocation, but a func statement. And the parameters are Int and Bool. And there's zero output to the console, where I've also tried (lldb) command script import lldb.macosx.heap and (lldb) malloc_info —type 0x... with no result. As mentioned, I tried Zombies and the other Xcode memory management diagnostics with no insight into why Address Sanitizer is crashing at a func statement with an EXC_BAD_ACCESS, and I'm not sure how to diagnose this further.
What have I missed? Thanks for any insights.
Edit: Eventually made progress by switching code around and looking for different results. The eventual 'solution' is illogical in that I can't figure out how it should logically create any different result, but it does. And since it offers no insight into the original question of how to diagnose the cause of the EXC_BAD_ACCESS, I won't belabor it further here. For now, it'll be a 'solved' mystery.