We are experiencing an issue where our app gets stuck during launch. The splash screen appears for some time, and then the app either becomes unresponsive or closes unexpectedly. However, there are no crash logs captured in Xcode or Firebase Crashlytics, indicating that the app is not crashing but rather being terminated. This issue is preventing affected users from properly launching the app. Additionally, some users have reported occasional lag and slow performance when using the app. The issue occurs only for a specific subset of users and appears to be related to other Electronic Logging Device (ELD) apps running in the background. When these apps are active, our app struggles to launch and sometimes becomes unresponsive. We suspect that this behavior could be related to system resource allocation, such as high memory consumption by background apps, which might be affecting our app's ability to launch correctly. However, we have been unable to reproduce the issue on our end despite multiple attempts. Actions Performed During App Launch: Firebase configuration API requests, including: Fetching account details Registering the FCM token with the server Asynchronous background requests to fetch POI details Creating a local database and storing POI data in local storage We would like guidance from Apple regarding potential causes and debugging strategies, especially in scenarios where the app does not produce crash logs but still fails to launch properly. Any insights into memory management, conflicts with background applications, or system resource constraints would be highly appreciated. Steps to Reproduce: Install and launch the app on an affected device. Observe that the app gets stuck on the launch screen. After some time, the app terminates unexpectedly. Issue is inconsistent and occurs only for certain users. Presence of other ELD apps running in the background appears to influence the issue.

I regularly bump into folks confused by this issue, so I thought I’d collect my thoughts on the topic into a single (hopefully) coherent post. If you have questions or comments, put them in a new thread here on the forums. Feel free to use whatever subtopic and tags that apply to your situation, but make sure to add the Debugging tag so that I see your thread go by. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Testing and Debugging Code Running in the Background I regularly see questions like this: My background code works just fine in Xcode but fails when I download the app from the App Store. or this: … or fails when I run my app from the Home screen. or this: How do I step through my background code? These suggest a fundamental misunderstanding of how the debugger interacts with iOS’s background execution model. The goal of this post is to explain that misunderstanding so that you can effectively test and debug background code. Note The focus of this post is iOS. The advice here generally applies to any of iOS’s ‘child’ platforms, so iPadOS, tvOS, and so on. However, there will be some platform specific differences, especially on watchOS. This advice here doesn’t apply to macOS. It’s background execution model is completely different than the one used by iOS. Understand the Fundamentals The key point to note here is that the debugger prevents your app from suspending. This has important consequences for iOS’s background execution model. Normally: iOS suspends your app when it’s in the background. Once your app is suspended, it becomes eligible for termination. The most common reason for this is that the system wants to recover memory, but it can happen for various other reasons. For example, the system might terminate a suspended app in order to update it. Under various circumstances your app can continue running after moving to the background. A great example of this is the continued processed task feature, introduced in iOS 26 beta. Alternatively, your app can be resumed or relaunched in the background to perform some task. For example, the region monitor feature of Core Location can resume or relaunch your app in the background when the user enters or leaves a region. If no app needs to be executing, the system can sleep the CPU. None of this happens in the normal way if the debugger is attached to your app, and it’s vital that you take that into account when debugging code that runs in the background. An Example of the Problem For an example of how this can cause problems, imagine an app that uses an URLSession background session. A background session will resume or relaunch your app in the background when specific events happen. This involves two separate code paths: If your app is suspended, the session resumes it in the background. If your app is terminated, it relaunches it in the background. Neither code path behaves normally if the debugger is attached. In the first case, the app never suspends, so the resume case isn’t properly exercised. Rather, your background session acts like it would if your app were in the foreground. Normally this doesn’t cause too many problems, so this isn’t a huge concern. On the other hand, the second case is much more problematic. The debugger prevents your app from suspending, and hence from terminating, and thus you can’t exercise this code path at all. Seek Framework-Specific Advice The above is just an example, and there are likely other things to keep in mind when debugging background code for a specific framework. Consult the documentation for the framework you’re working with to see if it has specific advice. Note For URLSession background sessions, check out Testing Background Session Code. The rest of this post focuses on the general case, offering advice that applies to all frameworks that support background execution. Run Your App Outside of Xcode When debugging background execution, launch your app from the Home screen. For day-to-day development: Run the app from Xcode in the normal way (Product > Run). Stop it. Run it again from the Home screen. Alternatively, install a build from TestFlight. This accurately replicates the App Store install experience. Write Code with Debugging in Mind It’s obvious that, if you run the app without attaching the debugger, you won’t be able to use the debugger to debug it. Rather: Extract the core logic of your code into libraries, and then write extensive unit tests for those libraries. You’ll be able to debug these unit tests with the debugger. Add log points to help debug your integration with the system. Treat your logging as a feature of your product. Carefully consider where to add log points and at what level to log. Check this logging code into your source code repository and ship it — or at least the bulk of it — as part of your final product. This logging will be super helpful when it comes to debugging problems that only show up in the field. My general advice is that you use the system log for these log points. See Your Friend the System Log for lots of advice on that front. One of the great features of the system log is that disabled log points are very cheap. In most cases it’s fine to leave these in your final product. Attach and Detach In some cases it really is helpful to debug with the debugger. One option here is to attach to your running app, debug a specific thing, and then detach from it. Specifically: To attach to a running app, choose Debug > Attach to Process > YourAppName in Xcode. To detach, choose Debug > Detach. Understand Force Quit iOS allows users to remove an app from the multitasking UI. This is commonly known as force quit, but that’s not a particularly accurate term: The multitasking UI doesn’t show apps that are running, it shows apps that have been run by the user. The UI shows recently run apps regardless of whether they’re in the foreground, running in the background, suspended, or terminated. So, removing an app from the UI may not actually quit anything. Removing an app sets a flag that prevents the app from being launched in the background. That flag gets cleared when the user next launches the app manually. Note In some circumstances iOS will not honour this flag. The exact cases where this happens are not documented and have changed over time. Keep these behaviours in mind as you debug your background execution code. For example, imagine you’re trying to test the URLSession background relaunch code path discussed above. If you force quit your app, you’ll never hit this code path because iOS won’t relaunch your app in the background. Rather, add a debug-only button that causes your app to call exit. IMPORTANT This suggestion is for debugging only. Don’t include a Quit button in your final app! This is specifically proscribed by QA1561. Alternatively, if you’re attached to your app with Xcode, simply choose Product > Stop. This is like calling exit; it has no impact on your app’s ability to run in the background. Test With Various Background App Refresh Settings iOS puts users in control of background execution via the options in Settings > General > Background App Refresh. Test how your app performs with the following settings: Background app refresh turned off overall Background app refresh turned on in general but turned off for your app Background app refresh turned on in general and turned on for your app IMPORTANT While these settings are labelled Background App Refresh, they affect subsystems other than background app refresh. Test all of these cases regardless of what specific background execution feature you’re using. Test Realistic User Scenarios In many cases you won’t be able to fully test background execution code at your desk. Rather, install a TestFlight build of your app and then use the device as a normal user would. For example: To test Core Location background execution properly, actual leave your office and move around as a user might. To test background app refresh, use your app regularly during the day and then put your device on charge at night. Testing like this requires two things: Patience Good logging The system log may be sufficient here, but you might need to investigate other logging solutions that are more appropriate for your product. These testing challenges are why it’s critical that you have unit tests to exercise your core logic. It takes a lot of time to run integration tests like this, so you want to focus on integration issues. Before starting your integration tests, make sure that your unit tests have flushed out any bugs in your core logic. Revision History 2025-08-12 Made various editorial changes. 2025-08-11 First posted.

Hi there, I am trying to create my first iOS app using Visual Studio (Win 11) and .NET MAUI. I created a developer account and if I want to start the debugger with my local device, VS forces me to Configure Automatic Provisioning. I can select my configured account but the operation fails (see screenshot). I have no idea what is going wrong and I cannot find any setting in the developer account to fix this problem. Can anyone help me out, what is wrong and how to fix, thx!

Hi, I am having an issue with xcodebuild -showdestinations command. Steps to reproduce: Create a new iOS application project in Xcode or use an existing one. Navigate to this project in a terminal. Run xcodebuild -project 'your-project-name.xcodeproj' -scheme 'your-scheme' -showdestinations What I expect: All destinations available in the Xcode UI should be listed. What I get: It depends. For new projects, I consistently get only generic platform destinations and my connected physical device. When I run the same command on an older project, I sometimes see all the expected destinations. It seems to be a roughly 50/50 chance between the two outcomes. Is there a way to get consistent results from xcodebuild -showdestinations? What can I do to ensure all destinations are listed reliably? Here is a more detailed log and a screenshot: ❯ xcodebuild -workspace 'WorkoutDiary.xcworkspace' -scheme 'WorkoutDiary' -showdestinations Command line invocation: /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -workspace WorkoutDiary.xcworkspace -scheme WorkoutDiary -showdestinations User defaults from command line: IDEPackageSupportUseBuiltinSCM = YES 2025-06-17 19:13:50.261 xcodebuild[34753:6177985] DVTDeviceOperation: Encountered a build number "" that is incompatible with DVTBuildVersion. 2025-06-17 19:13:50.342 xcodebuild[34753:6177959] [MT] DVTDeviceOperation: Encountered a build number "" that is incompatible with DVTBuildVersion. Resolve Package Graph Resolved source packages: <REDACTED> Available destinations for the "WorkoutDiary" scheme: { platform:macOS, arch:arm64, variant:Designed for [iPad,iPhone], id:<REDACTED>, name:My Mac } { platform:iOS, arch:arm64, id:<REDACTED>, name:<REDACTED> } { platform:iOS, id:dvtdevice-DVTiPhonePlaceholder-iphoneos:placeholder, name:Any iOS Device } { platform:iOS Simulator, id:dvtdevice-DVTiOSDeviceSimulatorPlaceholder-iphonesimulator:placeholder, name:Any iOS Simulator Device } ❯ xcodebuild -workspace 'WorkoutDiary.xcworkspace' -scheme 'WorkoutDiary' -showdestinations Command line invocation: /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -workspace WorkoutDiary.xcworkspace -scheme WorkoutDiary -showdestinations User defaults from command line: IDEPackageSupportUseBuiltinSCM = YES 2025-06-17 19:13:52.393 xcodebuild[34757:6178035] DVTDeviceOperation: Encountered a build number "" that is incompatible with DVTBuildVersion. 2025-06-17 19:13:52.472 xcodebuild[34757:6178020] [MT] DVTDeviceOperation: Encountered a build number "" that is incompatible with DVTBuildVersion. Resolve Package Graph Resolved source packages: <REDACTED> Available destinations for the "WorkoutDiary" scheme: { platform:macOS, arch:arm64, variant:Designed for [iPad,iPhone], id:<REDACTED>, name:My Mac } { platform:iOS, arch:arm64, id:<REDACTED>, name:<REDACTED> } { platform:iOS, id:dvtdevice-DVTiPhonePlaceholder-iphoneos:placeholder, name:Any iOS Device } { platform:iOS Simulator, id:dvtdevice-DVTiOSDeviceSimulatorPlaceholder-iphonesimulator:placeholder, name:Any iOS Simulator Device } { platform:iOS Simulator, id:DBFB9613-0261-4544-908A-335570F3C35F, OS:18.3.1, name:iPhone 11 } { platform:iOS Simulator, id:A48C309C-231A-4197-A295-900F89C94D86, OS:18.3.1, name:iPhone 16 Pro Max }

Hi, I’m currently developing a watchOS app and ran into an issue where I can’t enable Developer Mode on my Apple Watch. Device info: Apple Watch Series 9 (watchOS 10.4) Paired with iPhone 14 Pro (iOS 17.4.1) Xcode 15.3 (macOS 15.5, Apple Silicon) Issue: When I try to run the app on my physical watch device, Xcode prompts that Developer Mode needs to be enabled. However, there is no approval request on the Apple Watch, and no Developer Mode option appears under Settings → Privacy &amp; Security. I’ve already tried the following: Rebooting both devices Unpairing and re-pairing the watch Erasing and setting up the watch again Signing out and back into my Apple ID Using the latest Xcode version (15.3 and 16.3 both tested) Running clean builds and checking provisioning profiles Attempting install via both simulator and physical device Still no luck — the app will not launch on the Apple Watch due to Developer Mode being disabled, and the option is missing entirely from Settings. I visited an Apple Store Genius Bar, but they couldn’t help and told me to contact Developer Support. I’ve already submitted a support request, but in the meantime I wanted to ask here in case anyone else has experienced this and found a workaround. Thanks in advance.

We are developing a cross platform c++ application. We also use some objective-c (no swift) and specific Apple frameworks like AVFoundation, CoreML in the MacOs version of our software. We use Apple Clang as compiler when building for MacOs. As our code is primarily c++ we would like to use the latest and greatest c++ 20 features. So we are looking into using vanilla clang instead, the builds with vanilla clang seem to work fine, however our concern is that we might have overlooked possible issues that could arise. So our question is whether there are specific things we need to address when switching compilers, are there things that we need to be aware of? In the end we just want to know if switching compilers won't cause problems we can't oversee. So we would like to know if others took the same steps and what your thoughts/experiences are regarding this?

Hi All, I have an App on AppStore, recently the minimum supported version of the app was changed from iOS 12 to iOS 14. Post that the TestFlight builds are crashing on launch. If we revert the minimum supported iOS version to 12, the crash no longer happens. This project is using cocoapods, and from the crash logs it seems the issue with with PLCrashReporter framework. "EXC_CRASH" Termination reason: DYLD 9 weak-def symbol not found '__ZN7plcrash3PL_5async15dwarf_cfa_stateljiE10push_stateEv'. This issue is happening only on TestFlight builds where the minimum supported version is 14.0 Any pointer to a solution is welcome.

Hi, Some crashes downloaded from TestFlight aren't symbolicated by Xcode and I don't know why, here's an example: Although all uploaded builds contain debug symbols (Symbols directory with .symbols files) and other crashlogs in the same version are symbolicated just fine (also visible on the above SS). I have access only to the .symbols files but not to the original dSYMs and I wonder how to perform symbolication manually. I tried pointing atos and symbolicatecrash utilities to respective .symbols file, but they are unable to work with it. I'm sure it's possible as TestFlight symbolicates crashlogs using only .symbols files somehow. Could you give a hint?

Title basically explains what my issue is, from what I understand the only way to set an icon in an tauri app is using a icns file, I could be wrong but I don't know how to get macos theme changing stuff to work with it because of the icns file.

My application targets iOS 15+. Attempting to build and run it on my iPhone SE (orphaned at iOS 15.6) results in "Failed to prepare the device for development." I'm building with Xcode 15.2. What is the expected procedure here?

In our Unity App for iOS build, when we opened the PDF from the app, it is automatically opening in landspace mode instead of portrait. In the android and windows apps, we are able to open in the portrait mode. We tried to make the changes in the project settings but it did not change. Any way in which we can acheive this would be helpful for us.

First time user here. Trying to build my React-Native app on xcode. I keep getting "Could not build Module" and "missing package product" and tried many combination for my Podfile. I am on macbook pro M2, XCode version 16.2, building on iphone 16 v18.3.1. Pod version 1.16.2, react-native-cli:2.0.1, Here is my Podfile. I tried to assign modular_headers to individual Firebase packages but then I cant pod install. require_relative '../node_modules/react-native/scripts/react_native_pods' require_relative '../node_modules/@react-native-community/cli-platform-ios/native_modules' use_modular_headers! platform :ios, '18.0' prepare_react_native_project! target 'plana' do config = use_native_modules! use_react_native!( :path => config[:reactNativePath], :fabric_enabled => false, :app_path => "#{Pod::Config.instance.installation_root}/.." ) post_install do |installer| react_native_post_install( installer, config[:reactNativePath], :mac_catalyst_enabled => false, ) end end

Apple’s library technology has a long and glorious history, dating all the way back to the origins of Unix. This does, however, mean that it can be a bit confusing to newcomers. This is my attempt to clarify some terminology. If you have any questions or comments about this, start a new thread and tag it with Linker so that I see it. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" An Apple Library Primer Apple’s tools support two related concepts: Platform — This is the platform itself; macOS, iOS, iOS Simulator, and Mac Catalyst are all platforms. Architecture — This is a specific CPU architecture used by a platform. arm64 and x86_64 are both architectures. A given architecture might be used by multiple platforms. The most obvious example of this arm64, which is used by all of the platforms listed above. Code built for one platform will not work on another platform, even if both platforms use the same architecture. Code is usually packaged in either a Mach-O file or a static library. Mach-O is used for executables (MH_EXECUTE), dynamic libraries (MH_DYLIB), bundles (MH_BUNDLE), and object files (MH_OBJECT). These can have a variety of different extensions; the only constant is that .o is always used for a Mach-O containing an object file. Use otool and nm to examine a Mach-O file. Use vtool to quickly determine the platform for which it was built. Use size to get a summary of its size. Use dyld_info to get more details about a dynamic library. IMPORTANT All the tools mentioned here are documented in man pages. For information on how to access that documentation, see Reading UNIX Manual Pages. There’s also a Mach-O man page, with basic information about the file format. Many of these tools have old and new variants, using the -classic suffix or llvm- prefix, respectively. For example, there’s nm-classic and llvm-nm. If you run the original name for the tool, you’ll get either the old or new variant depending on the version of the currently selected tools. To explicitly request the old or new variants, use xcrun. The term Mach-O image refers to a Mach-O that can be loaded and executed without further processing. That includes executables, dynamic libraries, and bundles, but not object files. A dynamic library has the extension .dylib. You may also see this called a shared library. A framework is a bundle structure with the .framework extension that has both compile-time and run-time roles: At compile time, the framework combines the library’s headers and its stub library (stub libraries are explained below). At run time, the framework combines the library’s code, as a Mach-O dynamic library, and its associated resources. The exact structure of a framework varies by platform. For the details, see Placing Content in a Bundle. macOS supports both frameworks and standalone dynamic libraries. Other Apple platforms support frameworks but not standalone dynamic libraries. Historically these two roles were combined, that is, the framework included the headers, the dynamic library, and its resources. These days Apple ships different frameworks for each role. That is, the macOS SDK includes the compile-time framework and macOS itself includes the run-time one. Most third-party frameworks continue to combine these roles. A static library is an archive of one or more object files. It has the extension .a. Use ar, libtool, and ranlib to inspect and manipulate these archives. The static linker, or just the linker, runs at build time. It combines various inputs into a single output. Typically these inputs are object files, static libraries, dynamic libraries, and various configuration items. The output is most commonly a Mach-O image, although it’s also possible to output an object file. The linker may also output metadata, such as a link map (see Using a Link Map to Track Down a Symbol’s Origin). The linker has seen three major implementations: ld — This dates from the dawn of Mac OS X. ld64 — This was a rewrite started in the 2005 timeframe. Eventually it replaced ld completely. If you type ld, you get ld64. ld_prime — This was introduced with Xcode 15. This isn’t a separate tool. Rather, ld now supports the -ld_classic and -ld_new options to select a specific implementation. Note During the Xcode 15 beta cycle these options were -ld64 and -ld_prime. I continue to use those names because the definition of new changes over time (some of us still think of ld64 as the new linker ;–). The dynamic linker loads Mach-O images at runtime. Its path is /usr/lib/dyld, so it’s often referred to as dyld, dyld, or DYLD. Personally I pronounced that dee-lid, but some folks say di-lid and others say dee-why-el-dee. IMPORTANT Third-party executables must use the standard dynamic linker. Other Unix-y platforms support the notion of a statically linked executable, one that makes system calls directly. This is not supported on Apple platforms. Apple platforms provide binary compatibility via system dynamic libraries and frameworks, not at the system call level. Note Apple platforms have vestigial support for custom dynamic linkers (your executable tells the system which dynamic linker to use via the LC_LOAD_DYLINKER load command). This facility originated on macOS’s ancestor platform and has never been a supported option on any Apple platform. The dynamic linker has seen 4 major revisions. See WWDC 2017 Session 413 (referenced below) for a discussion of versions 1 through 3. Version 4 is basically a merging of versions 2 and 3. The dyld man page is chock-full of useful info, including a discussion of how it finds images at runtime. Every dynamic library has an install name, which is how the dynamic linker identifies the library. Historically that was the path where you installed the library. That’s still true for most system libraries, but nowadays a third-party library should use an rpath-relative install name. For more about this, see Dynamic Library Identification. Mach-O images are position independent, that is, they can be loaded at any location within the process’s address space. Historically, Mach-O supported the concept of position-dependent images, ones that could only be loaded at a specific address. While it may still be possible to create such an image, it’s no longer a good life choice. Mach-O images have a default load address, also known as the base address. For modern position-independent images this is 0 for library images and 4 GiB for executables (leaving the bottom 32 bits of the process’s address space unmapped). When the dynamic linker loads an image, it chooses an address for the image and then rebases the image to that address. If you take that address and subtract the image’s load address, you get a value known as the slide. Xcode 15 introduced the concept of a mergeable library. This a dynamic library with extra metadata that allows the linker to embed it into the output Mach-O image, much like a static library. Mergeable libraries have many benefits. For all the backstory, see WWDC 2023 Session 10268 Meet mergeable libraries. For instructions on how to set this up, see Configuring your project to use mergeable libraries. If you put a mergeable library into a framework structure you get a mergeable framework. Xcode 15 also introduced the concept of a static framework. This is a framework structure where the framework’s dynamic library is replaced by a static library. Note It’s not clear to me whether this offers any benefit over creating a mergeable framework. Earlier versions of Xcode did not have proper static framework support. That didn’t stop folks trying to use them, which caused all sorts of weird build problems. A universal binary is a file that contains multiple architectures for the same platform. Universal binaries always use the universal binary format. Use the file command to learn what architectures are within a universal binary. Use the lipo command to manipulate universal binaries. A universal binary’s architectures are either all in Mach-O format or all in the static library archive format. The latter is called a universal static library. A universal binary has the same extension as its non-universal equivalent. That means a .a file might be a static library or a universal static library. Most tools work on a single architecture within a universal binary. They default to the architecture of the current machine. To override this, pass the architecture in using a command-line option, typically -arch or --arch. An XCFramework is a single document package that includes libraries for any combination of platforms and architectures. It has the extension .xcframework. An XCFramework holds either a framework, a dynamic library, or a static library. All the elements must be the same type. Use xcodebuild to create an XCFramework. For specific instructions, see Xcode Help > Distribute binary frameworks > Create an XCFramework. Historically there was no need to code sign libraries in SDKs. If you shipped an SDK to another developer, they were responsible for re-signing all the code as part of their distribution process. Xcode 15 changes this. You should sign your SDK so that a developer using it can verify this dependency. For more details, see WWDC 2023 Session 10061 Verify app dependencies with digital signatures and Verifying the origin of your XCFrameworks. A stub library is a compact description of the contents of a dynamic library. It has the extension .tbd, which stands for text-based description (TBD). Apple’s SDKs include stub libraries to minimise their size; for the backstory, read this post. Use the tapi tool to create and manipulate stub libraries. In this context TAPI stands for a text-based API, an alternative name for TBD. Oh, and on the subject of tapi, I’d be remiss if I didn’t mention tapi-analyze! Stub libraries currently use YAML format, a fact that’s relevant when you try to interpret linker errors. If you’re curious about the format, read the tapi-tbdv4 man page. There’s also a JSON variant documented in the tapi-tbdv5 man page. Note Back in the day stub libraries used to be Mach-O files with all the code removed (MH_DYLIB_STUB). This format has long been deprecated in favour of TBD. Historically, the system maintained a dynamic linker shared cache, built at runtime from its working set of dynamic libraries. In macOS 11 and later this cache is included in the OS itself. Libraries in the cache are no longer present in their original locations on disk: % ls -lh /usr/lib/libSystem.B.dylib ls: /usr/lib/libSystem.B.dylib: No such file or directory Apple APIs, most notably dlopen, understand this and do the right thing if you supply the path of a library that moved into the cache. That’s true for some, but not all, command-line tools, for example: % dyld_info -exports /usr/lib/libSystem.B.dylib /usr/lib/libSystem.B.dylib [arm64e]: -exports: offset symbol … 0x5B827FE8 _mach_init_routine % nm /usr/lib/libSystem.B.dylib …/nm: error: /usr/lib/libSystem.B.dylib: No such file or directory When the linker creates a Mach-O image, it adds a bunch of helpful information to that image, including: The target platform The deployment target, that is, the minimum supported version of that platform Information about the tools used to build the image, most notably, the SDK version A build UUID For more information about the build UUID, see TN3178 Checking for and resolving build UUID problems. To dump the other information, run vtool. In some cases the OS uses the SDK version of the main executable to determine whether to enable new behaviour or retain old behaviour for compatibility purposes. You might see this referred to as compiled against SDK X. I typically refer to this as a linked-on-or-later check. Apple tools support the concept of autolinking. When your code uses a symbol from a module, the compiler inserts a reference (using the LC_LINKER_OPTION load command) to that module into the resulting object file (.o). When you link with that object file, the linker adds the referenced module to the list of modules that it searches when resolving symbols. Autolinking is obviously helpful but it can also cause problems, especially with cross-platform code. For information on how to enable and disable it, see the Build settings reference. Mach-O uses a two-level namespace. When a Mach-O image imports a symbol, it references the symbol name and the library where it expects to find that symbol. This improves both performance and reliability but it precludes certain techniques that might work on other platforms. For example, you can’t define a function called printf and expect it to ‘see’ calls from other dynamic libraries because those libraries import the version of printf from libSystem. To help folks who rely on techniques like this, macOS supports a flat namespace compatibility mode. This has numerous sharp edges — for an example, see the posts on this thread — and it’s best to avoid it where you can. If you’re enabling the flat namespace as part of a developer tool, search the ’net for dyld interpose to learn about an alternative technique. WARNING Dynamic linker interposing is not documented as API. While it’s a useful technique for developer tools, do not use it in products you ship to end users. Apple platforms use DWARF. When you compile a file, the compiler puts the debug info into the resulting object file. When you link a set of object files into a executable, dynamic library, or bundle for distribution, the linker does not include this debug info. Rather, debug info is stored in a separate debug symbols document package. This has the extension .dSYM and is created using dsymutil. Use symbols to learn about the symbols in a file. Use dwarfdump to get detailed information about DWARF debug info. Use atos to map an address to its corresponding symbol name. Different languages use different name mangling schemes: C, and all later languages, add a leading underscore (_) to distinguish their symbols from assembly language symbols. C++ uses a complex name mangling scheme. Use the c++filt tool to undo this mangling. Likewise, for Swift. Use swift demangle to undo this mangling. For a bunch more info about symbols in Mach-O, see Understanding Mach-O Symbols. This includes a discussion of weak references and weak definition. If your code is referencing a symbol unexpectedly, see Determining Why a Symbol is Referenced. To remove symbols from a Mach-O file, run strip. To hide symbols, run nmedit. It’s common for linkers to divide an object file into sections. You might find data in the data section and code in the text section (text is an old Unix term for code). Mach-O uses segments and sections. For example, there is a text segment (__TEXT) and within that various sections for code (__TEXT > __text), constant C strings (__TEXT > __cstring), and so on. Over the years there have been some really good talks about linking and libraries at WWDC, including: WWDC 2023 Session 10268 Meet mergeable libraries WWDC 2022 Session 110362 Link fast: Improve build and launch times WWDC 2022 Session 110370 Debug Swift debugging with LLDB WWDC 2021 Session 10211 Symbolication: Beyond the basics WWDC 2019 Session 416 Binary Frameworks in Swift — Despite the name, this covers XCFrameworks in depth. WWDC 2018 Session 415 Behind the Scenes of the Xcode Build Process WWDC 2017 Session 413 App Startup Time: Past, Present, and Future WWDC 2016 Session 406 Optimizing App Startup Time Note The older talks are no longer available from Apple, but you may be able to find transcripts out there on the ’net. Historically Apple published a document, Mac OS X ABI Mach-O File Format Reference, or some variant thereof, that acted as the definitive reference to the Mach-O file format. This document is no longer available from Apple. If you’re doing serious work with Mach-O, I recommend that you find an old copy. It’s definitely out of date, but there’s no better place to get a high-level introduction to the concepts. The Mach-O Wikipedia page has a link to an archived version of the document. For the most up-to-date information about Mach-O, see the declarations and doc comments in <mach-o/loader.h>. Revision History 2025-08-04 Added a link to Determining Why a Symbol is Referenced. 2025-06-29 Added information about autolinking. 2025-05-21 Added a note about the legacy Mach-O stub library format (MH_DYLIB_STUB). 2025-04-30 Added a specific reference to the man pages for the TBD format. 2025-03-01 Added a link to Understanding Mach-O Symbols. Added a link to TN3178 Checking for and resolving build UUID problems. Added a summary of the information available via vtool. Discussed linked-on-or-later checks. Explained how Mach-O uses segments and sections. Explained the old (-classic) and new (llvm-) tool variants. Referenced the Mach-O man page. Added basic info about the strip and nmedit tools. 2025-02-17 Expanded the discussion of dynamic library identification. 2024-10-07 Added some basic information about the dynamic linker shared cache. 2024-07-26 Clarified the description of the expected load address for Mach-O images. 2024-07-23 Added a discussion of position-independent images and the image slide. 2024-05-08 Added links to the demangling tools. 2024-04-30 Clarified the requirement to use the standard dynamic linker. 2024-03-02 Updated the discussion of static frameworks to account for Xcode 15 changes. Removed the link to WWDC 2018 Session 415 because it no longer works )-: 2024-03-01 Added the WWDC 2023 session to the list of sessions to make it easier to find. Added a reference to Using a Link Map to Track Down a Symbol’s Origin. Made other minor editorial changes. 2023-09-20 Added a link to Dynamic Library Identification. Updated the names for the static linker implementations (-ld_prime is no more!). Removed the beta epithet from Xcode 15. 2023-06-13 Defined the term Mach-O image. Added sections for both the static and dynamic linkers. Described the two big new features in Xcode 15: mergeable libraries and dependency verification. 2023-06-01 Add a reference to tapi-analyze. 2023-05-29 Added a discussion of the two-level namespace. 2023-04-27 Added a mention of the size tool. 2023-01-23 Explained the compile-time and run-time roles of a framework. Made other minor editorial changes. 2022-11-17 Added an explanation of TAPI. 2022-10-12 Added links to Mach-O documentation. 2022-09-29 Added info about .dSYM files. Added a few more links to WWDC sessions. 2022-09-21 First posted.

In Simulator Korean character system has not working well. I want to type "", however, if I type the same thing on the simulator's virtual keyboard (Korean), it comes out as ''. I think this is caused by IME system in ios simulator bug. I think this has been happening since IOS 17.

I am working on an iOS app and I want to achieve on demand module download inside the app when the user clicks on the module icon which he wants to use. The idea is that we have a super app consisting of multiple modules say four independent apps/features and I want to separate each one so that when the user selects a specific app/feature, it’s downloaded on demand and then opened directly within the same super app resulting in a lower app size initially I want to upload all the code of all modules to app store connect but when the user downloads the app, then only one module's code should be available to the user, the rest of the module's code should be downloaded when the user wants to use that module. I know apple restricts downloading new code but in my case I want to upload all the code to app store for review but just give option to the user to get rest of the code when needed. Any guidance, architectural advice, or example implementations would be highly appreciated.

When building an app with iOS26 beta3, I received a warning saying "Launch screens will soon be required." Does this mean that, similar to the thread below, the app might not launch in builds for iOS27 and later (including iOS27)? https://developer.apple.com/forums/thread/789004

Hi everyone! I change my iPhone but I don't find the voice to activate "Developer Mode". I remember that I activated this feature with my old Xs in few minutes. I don't understand.... I must add the 16 Pro and the new Watch 10 for testing in Xcode. How? Thanks!

I try to distribute my App again, but receive now the error that the Minimum IOS is not supported by Info.plist with Runner. i have latest XCode and the error stays whatever IOS I Set in General and in the building rules. Any one has an idea or had same issue since recent Xcode / project Updates ? thanks so much

Hello guys, I know people already talked about this here but maybe some of you solved it. When trying Alarmkit, it keeps playing the same default sound. I tried a lot of changes to make it play my custom sound but nothing worked. Has anyone solved this or is it just the alarmkit problem? Thank you and take care guys.

Hello guys, I have probleme with the lib react tinode on ios , someone can help m on it plz ?