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LLDB crash

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Reply to Hardware Memory Tag (MIE) enforcement outside of debugger
So, I have three bits of good news: My boss got me an iPhone 17 so that I can test this properly. Thanks boss! It was a public holiday in the US yesterday, which allowed me to catch up a bit, so I had some time to play with MIE today. I figured out the sequence to get soft mode crash reports (-: Here’s what I did: Using Xcode 26.2 on macOS 26.2 [1], I created a new project from the iOS > App template, choosing Objective-C as the language. In the view controller, I added this code: - (IBAction)testAction:(id)sender { char * buf = malloc(32); buf[16] += 1; free(buf); buf[16] += 1; } I added a Test button and wired it up to that action. In Signing & Capabilities, I added the Enhanced Security capability and checked all the boxes (-: In the scheme editor, I enabled Diagnostics > Hardware Memory Tagging. I selected an iPhone 17 running iOS 26.2 as my run destination and chose Product > Run. On the device, I tapped the Test button. It trapped, with Xcode highlighting the second increment. So f
Topic: Privacy & Security SubTopic: General Tags:
Jan ’26
URLRequest(url:cachePolicy:timeoutInterval:) started to crash in iOS 26
For a long time our app had this creation of a URLRequest: var urlRequest = URLRequest(url: url, cachePolicy: .reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: timeout) But since iOS 26 was released we started to get crashes in this call. It is created on a background thread. Thread 10 Crashed: 0 libsystem_malloc.dylib 0x00000001920e309c _xzm_xzone_malloc_freelist_outlined + 864 (xzone_malloc.c:1869) 1 libswiftCore.dylib 0x0000000184030360 swift::swift_slowAllocTyped(unsigned long, unsigned long, unsigned long long) + 56 (Heap.cpp:110) 2 libswiftCore.dylib 0x0000000184030754 swift_allocObject + 136 (HeapObject.cpp:245) 3 Foundation 0x00000001845dab9c specialized _ArrayBuffer._consumeAndCreateNew(bufferIsUnique:minimumCapacity:growForAppend:) + 120 4 Foundation 0x00000001845daa58 specialized static _SwiftURL._makeCFURL(from:baseURL:) + 2288 (URL_Swift.swift:1192) 5 Foundation 0x00000001845da118 closure #1 in _SwiftURL._nsurl.getter + 112 (URL_Swift.swift:64) 6 Foundation 0x00000001845d
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Jan ’26
Inconsistent Symbol Linking Behavior for UTType from UniformTypeIdentifiers Framework
In our app, we implement a document picker using FilePickerManager+available.m, selecting different APIs based on the iOS version: if (@available(iOS 14.0, *)) { NSMutableArray *contentTypes = [NSMutableArray array]; for (NSString *uti in documentTypes) { UTType *type = [UTType typeWithIdentifier:uti]; if (type) { [contentTypes addObject:type]; NSLog(@iOS 14+ Adding type: %@, uti); } else { NSLog(@Warning: Unable to create UTI: %@, uti); } } UIDocumentPickerViewController *documentPicker = [[UIDocumentPickerViewController alloc] initForOpeningContentTypes:contentTypes]; documentPicker.delegate = self; documentPicker.allowsMultipleSelection = NO; [self.presentingViewController presentViewController:documentPicker animated:YES completion:nil]; } However, we've observed inconsistent symbol reference types to UTType in the final linked binaries: One build results in a strong reference to UTType. Another demo project (with seemingly identical code and build settings) results in a weak reference. Both object files
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Jan ’26
Inconsistent Symbol Linking Behavior for UTType from UniformTypeIdentifiers Framework
In our app, we implement a document picker using FilePickerManager+available.m, selecting different APIs based on the iOS version: if (@available(iOS 14.0, *)) { NSMutableArray *contentTypes = [NSMutableArray array]; for (NSString *uti in documentTypes) { UTType *type = [UTType typeWithIdentifier:uti]; if (type) { [contentTypes addObject:type]; NSLog(@iOS 14+ Adding type: %@, uti); } else { NSLog(@Warning: Unable to create UTI: %@, uti); } } UIDocumentPickerViewController *documentPicker = [[UIDocumentPickerViewController alloc] initForOpeningContentTypes:contentTypes]; documentPicker.delegate = self; documentPicker.allowsMultipleSelection = NO; [self.presentingViewController presentViewController:documentPicker animated:YES completion:nil]; } However, we've observed inconsistent symbol reference types to UTType in the final linked binaries: One build results in a strong reference to UTType. Another demo project (with seemingly identical code and build settings) results in a weak reference. Both object files
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Jan ’26
Reply to NSStagedMigrationManager Merging Steps
There was a few issues here. None of which are documented very well. And all crash with the same error message. (1) My orginal .xcdatamodel file didn't have a Core Data Model Identifier. Which lead to a crash with NSCustomMigrationStage, even though the versionChecksum are different. (2) The steps passed into NSStagedMigrationManager are not clear or documented. But it appears that if you pass the first version of the model into the steps, it crashes. (3) I'm using manual code generation for the model classes. So my goal was to switch the model names, then switch them back, so I didn't have to change anything. For some reason, stepping through the one migration step per app launch instead of all at once allowed for a successful migration. But running all steps threw an error. Turns out I could just rename the model classes with the _v2 suffix, and the only thing I needed to update was the string in the fetch request. Overall, to resolve this I added a model version identifier I dupl
Jan ’26
Flutter iOS - EXC_BAD_ACCESS crash on cold start after app was killed, affects ~1-2% of users
Question: How to prevent Flutter app crash on iOS 18 during cold start when iOS traverses view hierarchy before Flutter engine is fully initialized? Help needed: Looking for a way to either delay iOS view hierarchy traversal or ensure Flutter is fully initialized before iOS lifecycle callbacks fire. Problem Summary Our Flutter app crashes on cold start for approximately 1-2% of iOS users. The crash occurs specifically on iOS and only under these exact conditions: When crash happens: User opens app and uses it normally ✅ User minimizes app (goes to background) ✅ User returns to app from background ✅ (works fine) User kills app from app switcher (swipe up to close) User taps app icon to launch again → CRASH ❌ Key observations: Crash is intermittent - app may open on 2nd, 3rd, or 5th attempt 100% reproducible on affected devices by repeating kill→launch cycle ~98% of users have no issues Environment Flutter: 3.38.3 Crash Logs (from Sentry) Crash
Topic: UI Frameworks SubTopic: UIKit
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Jan ’26
Xcode 26.2 fails building Flutter iOS app – xcode_backend.dart null exception
Hello, after updating macOS to 26.2 and Xcode to 26.2 (Build 17C52), I am unable to build a Flutter iOS application for the simulator. Environment: macOS 26.2 (darwin-arm64) Xcode 26.2 (17C52) Flutter 3.38.7 (stable) Dart 3.10.7 CocoaPods 1.16.2 Target device: iPhone 16e Simulator (iOS 26.x) Issue: The build fails during the Flutter Xcode build phase with this error: Unhandled exception: Null check operator used on a null value #0 Context._embedNativeAssets (file:///opt/homebrew/share/flutter/packages/flutter_tools/bin/xcode_backend.dart:341) Command PhaseScriptExecution failed with a nonzero exit code. Additional info: Runner target uses Pods-Runner.debug/profile/release.xcconfig correctly SUPPORTED_PLATFORMS = iphoneos iphonesimulator SDKROOT resolves to iPhoneOS26.2.sdk even when building for simulator Build Settings and Run Script phases are default Flutter-generated Issue occurs both via flutter run and directly from Xcode Project worked before macOS/Xcode update It appears Xcode 26.2 may be resolving SD
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Jan ’26
File Provider Extension Memory Limit of 20MB is really limiting
I have an iOS and macOS app that includes a file provider extension. on macOS is is perfect no issues anywhere. on iOS it works for small datasets or if I do read only operations. as soon as I try to do anything with larger files I quickly hit the 20MB limit. I have solved file transfers by using chunking but when it comes to listing a folder with a couple thousand files it instantly crashes the FPE with an OOM error. works ok up to 100 files but anything beyond that crashes. I know enumerate items supports batches however the initial load form say a webdav server that has no concept of pagination will always fail to load in pieces no matter what I do. This likely explains why WebDAV was never implemented on iOS. in any case can you possibly consider upgrading the memory limit for FPE's or provide some mechanism to call our full iOS app for more processing power in the background to handle requests on demand? I do not understand where 20MB is a reasonable number. even 100MB seems more reason
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Jan ’26
Reply to URLRequest(url:cachePolicy:timeoutInterval:) started to crash in iOS 26
@DTS Engineer we believe we have found out the problem now... We created a TSI and Apple suggested that we tried find the crashing code by isolation, i.e., pulling our code until the crash disappeared. With some effort we managed to make a small demo app where the crash occurred. We realised that we have a UIView, which is backed by CATiledLayer. But for this view we also had backgroundColor = .clear. Even without the view's draw(rect:) method the app could crash! Apple's TSI engineer explained that if you have a view that implements draw(rect:) then you should not set the background color at the same time! But we needed the background to be transparent, and so we found that setting isOpaque = false instead of setting the background color made the crash disappear! We still believe that UIKit shouldn't crash if you set the background color, which it didn't do prior to iOS 26 :)
Jan ’26
Regarding the deadline for adopting the UIScene life cycle
https://developer.apple.com/forums/thread/788293 In the above thread, I received the following response: When building with the SDK from the next major release after iOS 26, iPadOS 26, macOS 26 and visionOS 26, UIKit will assert that all apps have adopted UIScene life cycle. Apps that fail this assert will crash on launch. does this mean that there will be no app crashes caused by UIKit in iOS 26, but there is a possibility of app crashes when building with the SDK provided from iOS 27 onwards?
Topic: UI Frameworks SubTopic: UIKit Tags:
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Jan ’26
Reply to System Panic with IOUserSCSIParallelInterfaceController during Dispatch Queue Configuration
Hi Kevin, Thank you for your deep insight. Your theory matches our observed facts perfectly! I have just updated FB21636775 with the latest symbolicated crash log captured today (Jan 19). 1. Evidence of Concurrent Execution Conflict From the symbolicated backtrace, it is clear that at the moment of the crash: Thread 1 (AuxiliaryQueue): Is in the middle of executing UserCreateTargetForID (Frame 12). This RPC call has not yet returned to our DEXT. Thread 4 (Crashed Thread): Has already received the hardware interrupt for the first command (TEST UNIT READY) and is attempting to invoke the completion API. 2. Crash Characteristic Analysis The system encountered an Address size fault (Null dereference) at address 0x0000000000000008. This confirms your deduction: because UserCreateTargetForID is still pending on the AuxiliaryQueue and has not returned, the target-related objects or OSAction metadata in the kernel are not yet fully initialized. Attempting to invoke the action from
Topic: App & System Services SubTopic: Drivers Tags:
Jan ’26
Reply to Signing succeeds but validate fails with "Missing code-signing certificate"
In a code signature, the certificates act as a chain of trust [1]. The first certificate is the leaf, the next is the one that issued the leaf, and so on until you get to a root. Ah I see, did not realize this before but it makes perfect sense, thank you. ...the next thing to check is whether this is the right type of profile. Turns out it is not a distribution profile and this was the problem all along. The error message Missing code-signing certificate was a red-herring this whole time. What is interesting is that it appears that it used to work even though it shouldn't have, by virtue of the fact that these app builds are present in Testflight and the profile it was using dates from before those builds. Alas am unable to confirm that for certain as CI history is too shallow and we no longer have a copy of the app bundle to verify. At some point altool has stopped returning non-zero exit codes on failure so CI has been blind to the failures for some months now (probably since Xcode 26 I'm guessing). Thanks
Jan ’26
Reply to System Panic with IOUserSCSIParallelInterfaceController during Dispatch Queue Configuration
I have updated the Bug Report (FB21636775) with a new symbolicated crash log. OK. I have a totally new theory. Is it possible you're having an interrupt fire before you've completed full initialization, so you end up shuffling uninitialized data into the system? The crash log shows that you're in IOUserSCSIParallelInterfaceController::UserCreateTargetForID, so this is still very early in the startup process. I ask this, because an issue like this would explain both of these: (1) I attempted the over-retaining experiment you suggested (adding an extra retain() at the start of the loop and omitting release() in the ISR). Over retaining a valid object shouldn't actually do anything meaningful, as all you're doing is incrementing a simple integer counter. Eventually you might cause the counter to overrun, but that's not something that would happen immediately. It certainly shouldn't cause a kernel panic... The result was critical: it triggered an immediate Kernel Panic / Hard Reset every time. .
Topic: App & System Services SubTopic: Drivers Tags:
Jan ’26