A handful of my customers have reported a consistent freeze in my app (smells like either a thread deadlock or an infinite recursion to me). It's working properly for most people, but if 3 people are reporting it to me that says to me that probably 300 are experiencing it but staying quiet. It happens every time they take a certain kind of action. But it never happens to me so I can't figure out what is breaking. No crash is happening, so I'm not getting any reports via Firebase. It doesn't appear to be related to their data, because they can have someone else use a different device, login to their account, download all of their data, and then successfully do the thing that freezes 100% of the time on their original device. I've got one of these customers set up on TestFlight so I can send them test versions of the app with some debug collection code. I created my own version of a tracelog and write a line to a file whenever I start/end a function. I've added those tracelog calls to a bunch of methods and classes (but not all). The action that causes the freeze is when they tap Edit on a record. What's supposed to happen is that I modally present a nav controller containing an EditBlahViewController. The trace logs show that the EditBlahViewController gets through viewDidLoad, viewWillAppear, two rounds of viewWillLayoutSubviews/viewDidLayoutSubviews... but then never gets to viewDidAppear. I've tried updating more and more functions/classes with the tracelog calls, but I can't find any infinite recursions. I've added tracelogs to all calls involving dispatching to other threads (especially synchronous dispatches to the main thread) but I don't see any deadlocks. Every dispatch to main starts and ends properly and then goes on to the next thing. User is on iOS 16.6.1 with an iPhone 12. I don't know what else to try. How can I debug this at a distance and figure out where the problem is?

Hi! I have a xcode workspace with first objectiveC framework (let’s call it framework#1). This framework has some singletons (+(instancetype)shared using the dispatch_once idiom. This code is pretty straight forward and used everywhere : + (instancetype)shared { static dispatch_once_t onceToken; static OGAKeyManager *instance = nil; dispatch_once(&onceToken, ^{ instance = [[self alloc] init]; }); return instance; } I have a second framework (framework#2) in Swift that uses theses singletons (the framework#1 is added as do not embeed in the framework settings). And I have an application that uses both frameworks. If I make a breakpoint inside the dispatch_once alloc/init, I see that I enter 2 times : once when the shared method is called from framework#1 and another one when it’s called from framework#2. How is that even possible ? Isn't dispatch_once supposed to handle this ? I asked chatGPT, it points out to some objC/Swift interoperability, but honestly, I don't see what I can do to make it work correctly. There is no circular dependency (framwork#2 uses framwork#1, but framwork#1 has no clue of framwork#2 existence) Maybe it has something to do with sandbox, but I don't see how can it be. Does anyone experienced some weird behavior like this ? Thanks

In a thread titled “Avoid Dispatch Global Concurrent Queues” [1], Quinn links to a video from WWDC 2015 Session 718, “Building Responsive and Efficient Apps with GCD”. However, this video is not available from the Apple Developer Videos site; only a half dozen or so videos from 2015 are available. This same issue of the missing video came up about five years ago, when Quinn stated that the video had been mistakenly removed but had been restored. Now it’s gone again. :sad_face: Could this video be restored again, or at least its transcript? While I understand that Apple is focused on Swift concurrency, I need to maintain some Objective-C code that uses GCD, and in tracking down some performance issues, I would like to better understand the tradeoffs in the existing code and make improvements where I can. I don’t have the resources to reimplement the code in Swift right now. (More generally, why can't Apple just leave all these videos online indefinitely, for historical purposes at least? Couldn't the ones deemed “old and misleading” just be tagged with a banner like the legacy documentation has?) [1] I like to think of these valuable threads as “Quinn Technical Notes”; I have a page in my Notes app that holds links to the ones I’ve found.

I had 2 crash report from our customer. Both crash point is same but there is no my code on crash stack trace. How to fix this kind of crash problem. Thread 1 Crashed:: Dispatch queue: com.apple.root.background-qos 0 libsystem_kernel.dylib 0x7ff81b84922a __pthread_kill + 10 1 libsystem_pthread.dylib 0x7ff81b880f7b pthread_kill + 263 2 libsystem_c.dylib 0x7ff81b7caca5 abort + 123 3 libc++abi.dylib 0x7ff81b83b082 abort_message + 241 4 libc++abi.dylib 0x7ff81b82c23d demangling_terminate_handler() + 266 5 libobjc.A.dylib 0x7ff81b529023 _objc_terminate() + 96 6 libc++abi.dylib 0x7ff81b83a4a5 std::__terminate(void (*)()) + 8 7 libc++abi.dylib 0x7ff81b83a456 std::terminate() + 54 8 libdispatch.dylib 0x7ff81b701a58 _dispatch_client_callout + 28 9 libdispatch.dylib 0x7ff81b704500 _dispatch_continuation_pop + 463 10 libdispatch.dylib 0x7ff81b715dff _dispatch_source_invoke + 2184 11 libdispatch.dylib 0x7ff81b7116a2 _dispatch_root_queue_drain + 343 12 libdispatch.dylib 0x7ff81b711e4d _dispatch_worker_thread2 + 160 13 libsystem_pthread.dylib 0x7ff81b87dc9d _pthread_wqthread + 256 14 libsystem_pthread.dylib 0x7ff81b87cc67 start_wqthread + 15 This crash point is exactly same with this post. I do not throw C++ exception. https://developer.apple.com/forums/thread/725197

I see this warning when my app runs: Thread running at QOS_CLASS_USER_INTERACTIVE waiting on a lower QoS thread running at QOS_CLASS_DEFAULT. Investigate ways to avoid priority inversions This is true; I know what is going on. I'd like this other thread to have a higher priority. But how do I set the "QOS class" for a thread? Searching developer.apple.com for QOS_CLASS_USER_INTERACTIVE doesn't find much. It seems that dispatch queues have priorities, but in this case I have a thread, not a dispatch queue. Any ideas?

Below is some simple code that does nothing, saves nothing. Yet the memory usage keeps rising. Am I missing something or is this a bug? The code requires 6 core CPU minimum. ContentView.swift import SwiftUI import Combine struct ContentView: View { @EnvironmentObject var loopClass:LoopClass var body: some View { ProgressView(value: Float(loopClass.loop_count), total: Float(loopClass.max_loops) ).progressViewStyle(.circular).padding() Button("Run looper", action: { loopClass.loopFunc() } ) } } LoopClass.swift import Combine class LoopClass: ObservableObject { @Published var loop_count = 0 @Published var max_loops = 0 func loopFunc () { let loopSet = [ 1, 3, 5, 7, 11, 13 ] max_loops = Int(pow(Double(loopSet.count), 13.0)) print("max_loops = \(max_loops)") for loop13 in loopSet { DispatchQueue.global().async { for loop12 in loopSet { for loop11 in loopSet { for loop10 in loopSet { for loop9 in loopSet { for loop8 in loopSet { for loop17 in loopSet { for loop16 in loopSet { for loop5 in loopSet { for loop4 in loopSet { for loop3 in loopSet { for loop2 in loopSet { for loop1 in loopSet { DispatchQueue.main.async{ self.loop_count += 1 } } }}}}}}}}}}} } // DQ } // for loop13 } }