[nexuist]

I have been developing iOS apps since 2014, and was active in the jailbreaking scene before then. I don't believe any one person understands the entirety of what is going on when they launch an app. Remember, iOS is based on macOS, which is based on NeXTSTEP, last released in 1995!

iOS has been plagued by a whole host of bugs from the 90s and below. Remember effective Power? (https://apple.stackexchange.com/a/189064/364414) A Unicode memory allocation bug, the code for which was probably written decades ago and intended to run on a CRT monitor. I find it hard to believe anyone at Apple had interacted with that code since the initial iPhone release. Probably nobody at Apple in 2015 knew it existed. It's so unfathomably complicated.

[saagarjha]

I started working on iOS apps around that time as well, soon after I started programming. If you put your mind to it tracing the startup process of an iOS app is not actually as difficult as you think it is, especially if you skim things like “how does RunningBoard manage my app’s lifecycle?” or “is this launch being logged by CoreDuet?”. Also, FWIW, Core Text has several engineers working on it–text rendering is not a solved problem in the slightest–and is public API depended on directly by many apps.