I spend a lot of time here on DevForums. Over the years I’ve read many posts, both good and bad. This page is my attempt at writing down what makes a good one. Hopefully some of you will find it useful. Before you read this, read the official Apple Developer > Support > Developer Forums page. If you have questions or feedback about any of the points raised here, start a new thread in the Developer Tools & Services > Developer Forums subtopic. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Quinn’s Top Ten DevForums Tips Here are my top ten DevForums tips: Is DevForums right for you? Search before you ask Keep your expectations realistic Topic, subtopic, and tags Craft a quality post Prefer text over images Include details with your questions Crash reports Cross posting courtesy Resize screenshots Include a Spinal Tap reference Close your threads Think about your title Post URLs in the clear Many of these boil down to one word: Empathy. Think about the person who’s reading your post. Can they read it? Will they understand it? Will it help them? 1. Is DevForums right for you? To quote Apple Developer > Support > Developer Forums, the Apple Developer Forums (aka DevForums) are: a great place to post questions, exchange knowledge, and connect with fellow developers and Apple engineers on a variety of development topics. DevForums is focused on developer issues. That includes the APIs in Apple’s platform SDKs, Apple tools, developer-oriented Apple services like App Store Connect, and accessory development. If you have a user-level question, you’ll have more luck over in Apple Support Communities, run by Apple Support. DevForums is focused on Apple technologies. If you’re using a third-party tool or library, feel free to ask questions about it here, but you’re more likely to find folks with relevant expertise in that technology’s dedicated support channel. If you want to file a bug report, do that using Feedback Assistant. If you want to discuss a bug you’ve already filed, DevForums is a great place for that. Make sure to include your bug number in your post. For more hints and tips on the bug reporting process, see Bug Reporting: How and Why?. 2. Search before you ask DevForums has a history stretching back to 2015. Many questions have been asked and answered here. Before you start a thread, search the forums for similar threads. For details about the search syntax, see Apple Developer > Support > Developer Forums. For a quick summary, click in the search field. Remember that DevForums is world readable and thus indexed by Internet search engines. 3. Keep your expectations realistic DevForums is an informal support channel; no one is being paid to answer DevForums questions full time. Keep that in mind when you post. Apple provides a number of formal support channels. To request formal support, go to the Apple Developer > Contact Us page. One of those support channels is the code-level support provided by Apple Developer Technical Support (DTS). For more information about DTS, see Apple Developer > Support > Requesting Technical Support. Asking about Apple’s unannounced plans is unlikely to yield useful results. Apple folks can’t discuss The Future™, and non-Apple folks can only speculate. Apple folks can’t discuss Apple’s internal business practices. For example, we can’t answer why question — “Why did Apple do this?” or “Why hasn’t Apple done that?” — unless there’s existing documentation that offers an explanation. If you think Apple should do something differently, file a bug that explains what you’d like to see change and the rationale for that. Not everyone works the same hours as you do. DevForums is a worldwide community, so there are time zones to consider, but there’s also just individual preferences. This is especially relevant around weekends, where your reply on Friday may not be seen by other folks until Monday. Different folks use DevForums in different ways. Some folks lean in to the notification system, whereas others allocate certain times of the day, or the week, to help out. 4. Topic, subtopic, and tags DevForums organises threads by two attributes: A high-level topic and subtopic A fine-grained set of tags Folks willing to offer help often monitor a specific set of subtopics or tags, and only see threads with those attributes. To increase the odds of getting a response, choose your subtopic and tags carefully. The list of subtopics is immediately visible on the top-level page. For a list of tags and their descriptions, go to Developer > Support > Forums Tags. That’s a lot of tags! When choosing a subtopic, choose the most specific one. For example, if you have a question about SwiftUI, choose UI Frameworks > SwiftUI rather than Programming Languages > Swift. The latter is primarily focused on the Swift language itself. When choosing a tag, read the description of that tag. With so many tags there are inevitably cases where a tag doesn’t mean what you think it means. For example, the Exception Handling tag is about the rarely used Exception Handling framework, not about exception handling in general, and the description makes that clear. 5. Craft a quality post When replying, use a reply rather than a comment. Comments are best reserved for short messages, like “Thanks!” or “See this other thread.” IMPORTANT If you reply in the comments, other folks on the thread may not be notified of your reply. DevForums supports Markdown formatting, similar to that used on GitHub and by DocC. The editor UI has buttons for the most common things, like Bold and Italic, but don’t feel the need to limit yourself to that. Correct formatting is particularly important for preformatted text: Use the Inline Code button, which inserts single backquote delimiters (```), for inline text in code style: identifiers and so on. Use the Code Block button, which inserts triple backquote delimiters (`````), for blocks of text in code style: code snippets, logs, and so on. After submitting your post, look it over to make sure that it reads well. If not, you have a short window where you can edit the post to fix things. 6. Prefer text over images Don’t use screenshots for data that’s essentially textual, like code snippets and logs. For example, if you want to post a log message, include that as text rather than adding a screenshot. That makes it much easier for your readers to work with the text. Use the Code Block button, which inserts triple backquote delimiters (`````), to format blocks of text in code style. Reserve screenshots for situations where the issue is visual, for example: When discussing view layout problems When posting instructions to achieve some task in a GUI app, like Xcode 7. Include details with your questions When starting a thread, try to include all the relevant details in your post. If you skimp on these details, folks will have to reply asking for them, and that slows things down. Specifically, anticipate the following questions: What platform are you targeting? And what version of that platform? What version of Xcode are you using? What version of the OS are you testing on? What specific API are you using? What are the exact steps you took? If something failed, what are the symptoms of that failure? If an API returned an error, what was that error? If nothing failed, what results did you see? And what were you expecting? If you filed a bug, what was the bug number? Have you tried reproducing the issue in a small test project? What else have you tried? For more thoughts on this, see Tips on writing forums posts. Oh, and if you’re having a build problem, consider attaching a full build log. 8. Crash reports If you’re trying to get help with a crash, include a crash report. For advice on how to do that, see Posting a Crash Report. 9. Cross posting courtesy Don’t start multiple threads for the same issue. That just wastes everyones time. Sometimes this happens by accident. If that’s the case, add a comment to one of the threads redirecting folks to the other one. If you find a bunch of old threads that might be related to your issue, don’t post full replies to all of them. Pick a lead thread and post your full reply there, then reply on the other threads with a link to the lead thread. Alternatively, start a new thread and reply on all the old threads with a link to that. That’ll help focus the discussion on your specific issue. If you post your question to another support channel, provide a link to that in your DevForums question, and vice versa. That avoids folks working on a question that’s already been answered elsewhere. 10. Resize screenshots If your post includes an image, make sure it renders well. Screenshots from Retina displays are often ridiculously large. Use Preview to crop the screenshot and, if necessary, downsample it by 50% (using Tools > Adjust Size). 11. Include a Spinal Tap reference To be clear, this is a joke. While the occasional Spinal Tap reference is allowed, please don’t add one to all your posts (-: 12. Close your threads If someone replies with the answer you need, mark that as accepted. That gives them some credit and helps other folks with similar questions find that answer. If you find the answer by yourself, please post a short summary of what you did. Feel free to mark that as accepted. There’s no way to change the accepted answer. See this thread for specific advice. You can’t delete your own threads. If you accidentally post two copies of the same question, choose one as the primary and, in the other one, add a reply that links to it. Beyond that, see this thread for more advice. 13. Think about your title When creating a thread, think carefully about your title. Your title is your thread’s ‘marketing statement’, a way to entice folks to read your post. Try to summarise your issue in 15 words or less. Adding tags to your title makes it harder to read. Instead, add your tags with the tagging UI. See tip 4 for more on tags. 14. Post URLs in the clear DevForums has a list of websites you can link to at will. For example, it places no restrictions on links to Swift Forums. To link to a site that’s not on the allowlist, skip the Markdown link syntax and post your link in the clear. So, this won’t work: Apple is based in [Cupertino](https://www.cupertino.org). but this will: Apple is based in Cupertino. https://www.cupertino.org Revision History 2025-12-02 Tidied up and expanded tip 12. 2025-06-19 Made minor editorial changes. 2024-08-29 Added a link to Creating a test project. 2024-08-07 Add more hints to tip 7. 2024-05-27 Reworked tip 4 to account for the new topic and subtopic model. Made other minor editorial changes. 2023-11-16 Added a link to [Public and Private Tags][refPaPT]. 2023-02-22 Expanded tip 3. 2023-02-10 Added a note about why questions to tip 3 (another great suggestion from Scott). Added a link to Bug Reporting: How and Why?. 2023-01-09 Added a note about tags to tip 13. 2022-12-09 Expanded tip 12. 2022-08-22 Expanded tip 5 to explain why you shouldn’t reply in the comments. 2022-08-11 Expanded tip 9. 2022-06-17 Added tip 14. Updated the preamble to include a link to the main DevForums page. 2022-06-04 Added a discussion of unannounced plans to tip 3 (thanks to Scott). 2022-06-03 Added tip 13. 2022-05-24 Added tips suggested by Claude31 and Scott. 2022-05-23 First posted.

I tried to monitor the device's network status with Network framework code below. let networkMonitor = NWPathMonitor(requiredInterfaceType: .cellular) networkMonitor.pathUpdateHandler = { [weak self] path in     if path.status == .satisfied {         print("Cellular Satisfied")     } else {         print("Cellular Unsatisfied")     } } When I run the app in my iPhone(iOS 15.5) and turn cellular on/off, iPhone suddenly loses connection with XCode. Lost connection to the debugger on “...'s iPhone”. Domain: IDEDebugSessionErrorDomain Code: 12 Recovery Suggestion: Restore the connection to “...'s iPhone” and run “...” again, or if “...” is still running, you can attach to it by selecting Debug > Attach to Process > .... User Info: {     DVTErrorCreationDateKey = "2022-06-23 02:16:30 +0000";     IDERunOperationFailingWorker = DBGLLDBLauncher; } Analytics Event: com.apple.dt.IDERunOperationWorkerFinished : {     "device_model" = "iPhone13,2";     "device_osBuild" = "15.5 (19F77)";     "device_platform" = "com.apple.platform.iphoneos";     "launchSession_schemeCommand" = Run;     "launchSession_state" = 2;     "launchSession_targetArch" = arm64;     "operation_duration_ms" = 5861;     "operation_errorCode" = 12;     "operation_errorDomain" = IDEDebugSessionErrorDomain;     "operation_errorWorker" = DBGLLDBLauncher;     "operation_name" = IDEiPhoneRunOperationWorkerGroup;     "param_consoleMode" = 0;     "param_debugger_attachToExtensions" = 0;     "param_debugger_attachToXPC" = 1;     "param_debugger_type" = 5;     "param_destination_isProxy" = 0;     "param_destination_platform" = "com.apple.platform.iphoneos";     "param_diag_MainThreadChecker_stopOnIssue" = 0;     "param_diag_MallocStackLogging_enableDuringAttach" = 0;     "param_diag_MallocStackLogging_enableForXPC" = 1;     "param_diag_allowLocationSimulation" = 1;     "param_diag_gpu_frameCapture_enable" = 0;     "param_diag_gpu_shaderValidation_enable" = 0;     "param_diag_gpu_validation_enable" = 0;     "param_diag_memoryGraphOnResourceException" = 0;     "param_diag_queueDebugging_enable" = 1;     "param_diag_runtimeProfile_generate" = 0;     "param_diag_sanitizer_asan_enable" = 0;     "param_diag_sanitizer_tsan_enable" = 0;     "param_diag_sanitizer_tsan_stopOnIssue" = 0;     "param_diag_sanitizer_ubsan_stopOnIssue" = 0;     "param_diag_showNonLocalizedStrings" = 0;     "param_diag_viewDebugging_enabled" = 1;     "param_diag_viewDebugging_insertDylibOnLaunch" = 1;     "param_install_style" = 0;     "param_launcher_UID" = 2;     "param_launcher_allowDeviceSensorReplayData" = 0;     "param_launcher_kind" = 0;     "param_launcher_style" = 0;     "param_launcher_substyle" = 0;     "param_runnable_appExtensionHostRunMode" = 0;     "param_runnable_productType" = "com.apple.product-type.application";     "param_runnable_swiftVersion" = "5.6";     "param_runnable_type" = 2;     "param_testing_launchedForTesting" = 0;     "param_testing_suppressSimulatorApp" = 0;     "param_testing_usingCLI" = 0;     "sdk_canonicalName" = "iphoneos15.4";     "sdk_osVersion" = "15.4";     "sdk_variant" = iphoneos; } In my opinion, it seems like an error of XCode. Plz let me know if there's any solution. Also, there's a similar issue here : https://developer.apple.com/forums/thread/681459

Hello, Switching Core Data Editor Style has been broken since Xcode 14 Beta 1. Although I can get by, it would be convenient to switch to the Graphical ER diagram style to "visually" study the model for an App. Regards and Thank You, John

I have written a small iOS app that I run as a MacOS app using the build target "My Mac (Designed for iPad)". It runs fine, however I cannot find where the app itself is installed on my system. When running the app multiple times I see that a number is appended to the title of my app is incremented indicating that old versions of the app are still installed somewhere. Where are they located on my system? Many thanks for the help!

I file a lot of bug reports. I also ask a lot of third-party developers to file bug reports about problems they see. This post is my attempt at collecting together some hints and tips about Apple’s bug reporting process. To file a bug report, use Feedback Assistant. To file an enhancement request, use Feedback Assistant. In the “What type of issue are you reporting?” popup, choose Suggestion. If you’re filing a bug against an API, choose Developer Technologies & Resources at the top level. The technologies popup should then list familiar items, from Accelerate Framework to XPC. If you can’t find the correct item, select “Something else not on this list”. Feedback Assistant is both a website and an app. For details on how to access the app, see Opening the app on the Developer > Bug Reporting page. For lots of great hints and tips about filing bugs, see File effective bug reports. I may repeat some of the info covered by that article, but only where I think it’s particularly important. After filing a bug report, please include the bug number in your DevForums post. Feedback Assistant shows the bug number in both the bug list and the bug detail view. Bug numbers start with FB and continue with a sequence of digits. For example, a recent bug report posted here on DevForums was FB11357055. Including the FB prefix avoids any confusion as to what type of bug number this is. Occasionally you’ll see other types of bug numbers. In release notes they are just in parens, so (99071807), and in DTS documents they have an r. prefix, so (r. 99071807). These are Radar numbers. Radar is the internal bug system here at Apple. Other developers can’t see your bug report. However, posting the bug number is still important for a couple of reasons: It allows Apple folks to quickly track down your issue. If another developer wants to file a related bug, they can reference your bug number in their bug report. You can share bug reports with other members of your team. For details on how to do that, see Collaborating with your team on the Developer > Bug Reporting page. Otherwise you can’t see a bug report filed by another developer, or one filed internally at Apple. One option here is to file your own bug and request that it be marked as a duplicate of the original bug. You’ll then be notified when the original bug is closed. The File effective bug reports article discusses the importance of including a sysdiagnose log with your bug report. I have a few additional tips: Include a sysdiagnose log from the machine that’s having the problem. Sometimes I see folks with an iOS problem include a sysdiagnose log for their development Mac )-: Include a sysdiagnose log even if you attach a test project that reproduces the problem. The contents of the log help with screening, making sure that your bug gets to the right person quickly. And that person will be very grateful to have your test project! If multiple machines are involved — for example, you’re reporting a Handoff problem — include a sysdiagnose log from each machine. Trigger the sysdiagnose log as soon as possible after you see the problem. The sooner you trigger the log, the more likely it is to capture relevant info. If the problem is hard to reproduce, see Using a Sysdiagnose Log to Debug a Hard-to-Reproduce Problem for hints on how to capture an actionable sysdiagnose log. If you install a debug profile, install it before you reproduce the problem. These profiles typically enable more logging, and you want that logging to be active at the time of the problem. Most profiles activate immediately but some require that you restart. Follow the instructions that came with the profile. When reproducing the problem, make a rough note of the time and include that in your bug report. This doesn’t have to be super precise. Just note down the time, with seconds, shortly after you reproduce the problem. If the bug involves a crash, reproduce the crash outside of Xcode and then take your sysdiagnose log. This means running your code as the user would, so running an app from the Finder on macOS, running an app from the Home screen on iOS, and so on. If you reproduce the crash inside Xcode, the Xcode debugger catches the crash and prevents the system from generating a crash report to include in the sysdiagnose log. File focused bug reports. Imagine you’re seeing two problems, A and B, related to the same API. Don’t file a single bug that covers both A and B. Rather, file separate bugs for A and B. Feel free to reference your A bug in your B bug, and vice versa. Finally, some personal notes: DevForums is not an official support channel. Mentioning a problem here is not the same as filing a bug about it. That’s true even if you’re discussing your issue with an Apple person. Apple is a big company, and it’s very unlikely that the person you’re talking to is directly responsible for fixing your bug. Historically I used to post a lot of Radar links, of the forms rdar:nnn, where nnn includes the bug number. I no longer use these links because I’ve found that they confuses folks. They click the link and wonder why it does nothing. If you post an FB number here, DevForums automatically turns it into a link. However, that link is only useful to you. Other folks can’t access the bug via that link. I’ve filed a bug against DevForums requesting that it only generate this link for the bug’s originator (r. 92946014). In the meantime, I work around this by putting FB numbers in code style, which disables this link generation. If you want to share bug information outside of DevForums, one popular option is Open Radar (https://openradar.appspot.com/). Apple uses a lot of open source and many open source projects maintain their own bug tracker. Two big examples are Swift and WebKit. If your bug originates in such an open source project, consider filing it in the project’s bug tracker. You can then go on to submit a pull request with the fix (-: Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Revision History 2025-08-07 Updated “Developer Technologies & SDKs” to “Developer Technologies & Resources”. 2024-03-07 Made minor editorial changes. 2023-10-26 Added a link to Using a Sysdiagnose Log to Debug a Hard-to-Reproduce Problem. Added a recommendation to file focused bug reports. 2023-06-28 Updated the advice on how to file an API-level bug based on recent changes to Feedback Assistant. Corrected some link titles. 2023-03-21 Added a bunch of bullets to the personal notes section. 2023-03-13 Extended the discussion of seeing other folks’ bugs to make it clear that you can’t see bugs filed internally at Apple. 2022-12-13 Added advice about the “Something else not on this list” option. 2022-09-01 Added a personal notes section at the end. Added a new bullet in the sysdiagnose section about running your app outside of Xcode. Made other minor editorial changes. 2022-08-29 Added a note about filing duplicate bugs. 2022-08-24 First posted.

Every time my app runs in the simulator I see this error: Warning: Error creating LLDB target at path '/Users/aaronsmith/Library/Developer/Xcode/DerivedData/Babylist-ahvzjxxrpawwqhecszqeyvjstfca/Build/Products/Debug-iphonesimulator/Babylist.app'- using an empty LLDB target which can cause slow memory reads from remote devices: the specified architecture 'arm64--' is not compatible with 'x86_64-apple-ios13.2.0-simulator' in '/Users/aaronsmith/Library/Developer/Xcode/DerivedData/Babylist-ahvzjxxrpawwqhecszqeyvjstfca/Build/Products/Debug-iphonesimulator/Babylist.app/Babylist' What is this? I'm on an M1, no build issues. It makes me think the simulator is running under rosetta with x68_64. But I didn't choose to do that. Mac OS Ventura. Xcode 14 RC.

Show dialog content "Unable to find a team with the given Team ID 'R6A82WMBSC' to which you belong. Please contact Apple Developer Program Support. https://developer.apple.com/support" when open "https://developer.apple.com/account/resources"

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.

With Xcode 14, the device selection on the bottom of the storyboard canvas has changed, and the iPhone 12 and 13 mini screens are no longer there, as well as there only being one model of iPad. Is there a way to add more devices to this section? I have simulators installed for these devices, and this is the way I've been checking compatibility so far, but this is not sustainable. I appreciate any help that you can give me.

I am developing CarPlay addition on our app. Which is distributed with the Enterprise In distribution method, so we do not have a product in the App Store. I am wondering if CarPlay support can be provided in applications distributed with the Enterprise in distribution method? If this is not possible, I will inform management that this is not possible. I am waiting for your answers, thanks.

I have an iPhone 14 running iOS 16.1 and my series 5 watch running watchOS 9.1. I was able to turn on Developer Mode on the phone by going to Settings--> Privacy & Security --> Developer Mode. On the watch however (I'm doing this directly on the watch and not on the watch app on the phone) once I'm in Privacy & Security, there is no option to select Developer Mode. How do I get my watch in Developer Mode in order to get a successful build in xCode?

I've been happily building and deploying my app to my iPhone and Watch S8, and the app was ready to submit to App Store Connect last night. However, when archiving it I got an error saying that my DynamicEventSelectionIntent was in multiple extensions. It was, kind of. When I started working on the complications I copied the Widgets intents into the complications, and left the name the same, but they were not in multiple targets. It looks like the info plist only had one item in the IntentsSupported (because they're the same name), so I decided to rename them so I had a widget one and a complications one. The problem I have now is that I can't deploy to my iPhone and Watch anymore because I'm getting this error: This app contains a WatchKit app with one or more Siri Intents app extensions that declare IntentsSupported that are not declared in any of the companion app's Siri Intents app extensions. WatchKit Siri Intents extensions' IntentsSupported values must be a subset of the companion app's Siri Intents extensions' IntentsSupported values. All I've done is rename one intent, and locate every instance of it in the info plist files, and add the appropriate new one into the right places. Here's what I've got. Main App contains Widget and WidgetIntentHandler, plus Watch App, which contains Complications and ComplicationsIntentHandler. Target: Main app: (I've removed everything that has no bearing on extensions.) Target: Widget: Target: WidgetIntentHandler: Target: Watch App: Target: Complications: Target: ComplicationsIntentHandler: Please, can someone tell me what should and should not be in the various parts, as I've tried for 12 hours now and I cannot get this to deploy to my iPhone anymore :( Thanks.

It's maddening. I just opened a file and now it's gone because I had the audacity to open another file. I've learned that I can double click the tab of the first file to make it a permanent tab... but, of course, I'll need to do that every time I ever open any file ever, and if I close that file and come back to it later I'm going to be constantly having to double click tabs just to make Xcode stop replacing my tabs for me. It's nuts. It's driving me insane. Please. Is there any way to just DISABLE the temporary tabs behavior? I don't find it helpful in any way and I find it to be destructive to my development workflows.

I have had this notice for a while: Registration is being processed for these devices. They may become available for development and ad hoc distribution in 24 to 72 hours. Changes to device availability will appear in the Status column. The status for my new iPhone has been stuck in this "Processing" state. See image:

Recently, I have trouble with my Xcode Cloud builds, where they seemingly complete, but the very final step does not happen. I am building from the same codebase for both macOS and iOS (I have two “Archive” steps in my workflow, one for iOS and one for macOS). The iOS one usually completes fast without problems. The macOS log ending looks like this, and remains stuck forever, with the macOS build in the “spinning progress” state and never completing. Is there something I can do on my end to make this work better? I would not want to go back to manual builds, Xcode Cloud is convenient and was working well for a while, but this is really annoying lately.

Is there a way to use CFBundleVersion instead of CI_BUILD_NUMBER from XCode Cloud's workflow on Web ? We would like to have control over the major and minor version numbers of the build from the workflow.

Each year I get my renewal email from Apple, however, since 2019 (yes, this is the 4th year in a row) I've been unable to renew due to this infamous "Please enter fewer characters" error message. Each time I've had to open a support case, talk to someone on the phone, they take all of my details along with screenshots, etc. and manually renew my subscription. Once they've charged my card I never hear from them again and issue never gets resolved. IDK if any Apple Dev Support folks actually use this forum but this is ridiculous.

When I try to run a simple executable from Cmake, I get this error. dyld[5005]: dyld cache '(null)' not loaded: syscall to map cache into shared region failed dyld[5005]: Library not loaded: /usr/lib/libSystem.B.dylib Referenced from: <7EB1C677-BB05-338C-8B29-CC2803CB8C21> /Users/pop/Desktop/Lang Reason: tried: '/usr/lib/libSystem.B.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/usr/lib/libSystem.B.dylib' (no such file), '/usr/lib/libSystem.B.dylib' (no such file, no dyld cache), '/usr/local/lib/libSystem.B.dylib' (no such file) I have tried looking for my file sudo find / -name libSystem.B.dylib but not luck. I am using an M1 chip and Ventura 13.1. Please ask for more details if you need them, as I really have no idea what to do about my problem.

We are building a framework which will be used by other apps. Want to integrate crash reporting and diagnostics for our framework. Want to report crashes to our backend happening inside our framework only and ignore app level crashes. Is it possible to filter crashes like that ?

Hi I've downloaded the latest version of Xcode 14.2 but when I run the app in Simulator I can only test it on iOS16.2 Is there a way to run it in 16.3?