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, dynamic libraries, bundles, and object files. 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. Stub libraries currently use YAML format, a fact that’s relevant when you try to interpret linker errors. Use the tapi tool to create and manipulate these files. 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! 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. 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. 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 2025-03-01 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.

I often find myself helping folks with dynamic library problems. These problems manifest in many different ways, but they all have one common factor: The dynamic library has an atypical install name. Sometimes this was inherited from macOS’s deep past, but most often it’s because folks aren’t aware of the two well-trodden paths through this particular minefield. This post is my attempt to rectify that. If you have questions or comments about this, start a new thread here on DevForums. 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" Dynamic Library Identification Apple’s dynamic linker has a lot of flexibility. Much of this flexibility exists for historical reasons, and it’s better for modern programs to follow one of two well-trodden paths: Most dynamic libraries should use an rpath-relative install name, as explained in Dynamic Library Standard Setup for Apps. In some cases it might make sense to use a full path for your install name, per Dynamic Library Full Path Alternative. To understand these options, you need to know a little bit about how the dynamic linker works, which is the subject of this post. Note This post covers some of the same ground as Embedding nonstandard code structures in a bundle, but in a less official way (-: Install Name Every dynamic library has an install name. This name identifies the library to the dynamic linker. When you link to a dynamic library, the static linker records the library’s install name in your Mach-O image. When the dynamic linker loads your Mach-O image, it uses those recorded install names to find and load the libraries you depend on. Note There are many different aliases for the term install name, including id, identification name, or install path. To see a library’s install name, run otool and examine the LC_ID_DYLIB load command: % otool -l libWaffle.dylib | grep -A 2 LC_ID_DYLIB cmd LC_ID_DYLIB cmdsize 48 name @rpath/libWaffle.dylib … Note The Mach-O load commands and their associated structures are defined in <mach-o/loader.h>. For example LC_ID_DYLIB is associated with the dylib_command structure. To see the install names of the libraries imported by a Mach-O image, run otool and examine the LC_LOAD_DYLIB load commands: % otool -l libVarnish.dylib | grep -A 2 LC_LOAD_DYLIB cmd LC_LOAD_DYLIB cmdsize 48 name @rpath/libWaffle.dylib … -- cmd LC_LOAD_DYLIB cmdsize 56 name /usr/lib/libSystem.B.dylib … Alternatively, use the -L option: % otool -L libVarnish.dylib … @rpath/libVarnish.dylib … @rpath/libWaffle.dylib … /usr/lib/libSystem.B.dylib … This displays the library’s own install name first, followed by the install names of all the libraries it imports. If you’re building a dynamic library with Xcode, use the Dynamic Library Install Name build setting to set the install name. If you’re building from the command line, pass the -install_name option to ld. For more about this, see the ld man page. It’s best to set the install name at build time and not change it. However, if you’re working with an existing dynamic library that has the wrong install name, you can usually change it using install_name_tool. See the install_name_tool man page for details. Runtime Path List Way back in the day, a dynamic library’s install name was the full path of the installed library. That’s why it’s called the install name. However, full paths don’t work in some situations. For example, if you have a library embedded within an app, you can’t use an full path because the app might not be installed in the Applications folder. To address this problem Apple updated the dynamic linker to support a number of special install name prefixes. At runtime it replaces the prefix with an appropriate path. For example, @executable_path is replaced with the path to the directory containing the processes main executable. For a full list of these prefixes see the dyld man page. However, if you’re creating a dynamic library you’ll want to focus on the runtime path, @rpath, or just rpath for short. The exact details of how this works are complex, see the man page for the full story, but the basic gist is that: The dynamic linker maintains a list of rpath directories. When it loads a Mach-O image, the dynamic linker looks for LC_RPATH load commands in the image. For each one it finds, it adds a new directory to the rpath list. When a Mach-O image imports a library with an rpath-relative install name, the dynamic linker searches for that library in each directory in the list. This may sound a bit abstract, so you might want to hop on over to Dynamic Library Standard Setup for Apps for some examples of how this works in practice. If you’re building a Mach-O image with Xcode, use the Runpath Search Paths build setting to add rpath directories. If you’re building from the command line, pass the -rpath option to ld. For more about this, see the ld man page. It’s best to configure your rpath directories at build time. However, if you’re working with an existing Mach-O that has the wrong rpath directories, you can add, delete, and change them using install_name_tool. See the install_name_tool man page for details.

This posts collects together a bunch of information about the symbols found in a Mach-O file. It assumes the terminology defined in An Apple Library Primer. If you’re unfamiliar with a term used here, look there for the definition. If you have any questions or comments about this, start a new thread in the Developer Tools & Services > General topic area and tag it with Linker. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Understanding Mach-O Symbols Every Mach-O file has a symbol table. This symbol table has many different uses: During development, it’s written by the compiler. And both read and written by the linker. And various other tools. During execution, it’s read by the dynamic linker. And also by various APIs, most notably dlsym. The symbol table is an array of entries. The format of each entry is very simple, but they have been used and combined in various creative ways to achieve a wide range of goals. For example: In a Mach-O object file, there’s an entry for each symbol exported to the linker. In a Mach-O image, there’s an entry for each symbol exported to the dynamic linker. And an entry for each symbol imported from dynamic libraries. Some entries hold information used by the debugger. See Debug Symbols, below. Examining the Symbol Table There are numerous tools to view and manipulate the symbol table, including nm, dyld_info, symbols, strip, and nmedit. Each of these has its own man page. A good place to start is nm: % nm Products/Debug/TestSymTab U ___stdoutp 0000000100000000 T __mh_execute_header U _fprintf U _getpid 0000000100003f44 T _main 0000000100008000 d _tDefault 0000000100003ecc T _test 0000000100003f04 t _testHelper Note In the examples in this post, TestSymTab is a Mach-O executable that’s formed by linking two Mach-O object files, main.o and TestCore.o. There are three columns here, and the second is the most important. It’s a single letter indicating the type of the entry. For example, T is a code symbol (in Unix parlance, code is in the text segment), D is a data symbol, and so on. An uppercase letter indicates that the symbol is visible to the linker; a lowercase letter indicates that it’s internal. An undefined (U) symbol has two potential meanings: In a Mach-O image, the symbol is typically imported from a specific dynamic library. The dynamic linker connects this import to the corresponding exported symbol of the dynamic library at load time. In a Mach-O object file, the symbol is undefined. In most cases the linker will try to resolve this symbol at link time. Note The above is a bit vague because there are numerous edge cases in how the system handles undefined symbols. For more on this, see Undefined Symbols, below. The first column in the nm output is the address associated with the entry, or blank if an address is not relevant for this type of entry. For a Mach-O image, this address is based on the load address, so the actual address at runtime is offset by the slide. See An Apple Library Primer for more about those concepts. The third column is the name for this entry. These names have a leading underscore because that’s the standard name mangling for C. See An Apple Library Primer for more about name mangling. The nm tool has a lot of formatting options. The ones I use the most are: -m — This prints more information about each symbol table entry. For example, if a symbol is imported from a dynamic library, this prints the library name. For a concrete example, see A Deeper Examination below. -a — This prints all the entries, including debug symbols. We’ll come back to that in the Debug Symbols section, below. -p — By default nm sorts entries by their address. This disables that sort, causing nm to print the entries in the order in which they occur in the symbol table. -x — This outputs entries in a raw format, which is great when you’re trying to understand what’s really going on. See Raw Symbol Information, below, for an example of this. A Deeper Examination To get more information about each symbol table, run nm with the -m option: % nm -m Products/Debug/TestSymTab (undefined) external ___stdoutp (from libSystem) 0000000100000000 (__TEXT,__text) [referenced dynamically] external __mh_execute_header (undefined) external _fprintf (from libSystem) (undefined) external _getpid (from libSystem) 0000000100003f44 (__TEXT,__text) external _main 0000000100008000 (__DATA,__data) non-external _tDefault 0000000100003ecc (__TEXT,__text) external _test 0000000100003f04 (__TEXT,__text) non-external _testHelper This contains a world of extra information about each entry. For example: You no longer have to remember cryptic single letter codes. Instead of U, you get undefined. If the symbol is imported from a dynamic library, it gives the name of that dynamic library. Here we see that _fprintf is imported from the libSystem library. It surfaces additional, more obscure information. For example, the referenced dynamically flag is a flag used by the linker to indicate that a symbol is… well… referenced dynamically, and thus shouldn’t be dead stripped. Undefined Symbols Mach-O’s handling of undefined symbols is quite complex. To start, you need to draw a distinction between the linker (aka the static linker) and the dynamic linker. Undefined Symbols at Link Time The linker takes a set of files as its input and produces a single file as its output. The input files can be Mach-O images or dynamic libraries [1]. The output file is typically a Mach-O image [2]. The goal of the linker is to merge the object files, resolving any undefined symbols used by those object files, and create the Mach-O image. There are two standard ways to resolve an undefined symbol: To a symbol exported by another Mach-O object file To a symbol exported by a dynamic library In the first case, the undefined symbol disappears in a puff of linker magic. In the second case, it records that the generated Mach-O image depends on that dynamic library [3] and adds a symbol table entry for that specific symbol. That entry is also shown as undefined, but it now indicates the library that the symbol is being imported from. This is the core of the two-level namespace. A Mach-O image that imports a symbol records both the symbol name and the library that exports the symbol. The above describes the standard ways used by the linker to resolve symbols. However, there are many subtleties here. The most radical is the flat namespace. That’s out of scope for this post, because it’s a really bad option for the vast majority of products. However, if you’re curious, the ld man page has some info about how symbol resolution works in that case. A more interesting case is the -undefined dynamic_lookup option. This represents a halfway house between the two-level namespace and the flat namespace. When you link a Mach-O image with this option, the linker resolves any undefined symbols by adding a dynamic lookup undefined entry to the symbol table. At load time, the dynamic linker attempts to resolve that symbol by searching all loaded images. This is useful if your software works on other Unix-y platforms, where a flat namespace is the norm. It can simplify your build system without going all the way to the flat namespace. Of course, if you use this facility and there are multiple libraries that export that symbol, you might be in for a surprise! [1] These days it’s more common for the build system to pass a stub library (.tbd) to the linker. The effect is much the same as passing in a dynamic library. In this discussion I’m sticking with the old mechanism, so just assume that I mean dynamic library or stub library. If you’re unfamiliar with the concept of a stub library, see An Apple Library Primer. [2] The linker can also merge the object files together into a single object file, but that’s relatively uncommon operation. For more on that, see the discussion of the -r option in the ld man page. [3] It adds an LC_LOAD_DYLIB load command with the install name from the dynamic library. See Dynamic Library Identification for more on that. Undefined Symbols at Load Time When you load a Mach-O image the dynamic linker is responsible for finding all the libraries it depends on, loading them, and connecting your imports to their exports. In the typical case the undefined entry in your symbol table records the symbol name and the library that exports the symbol. This allows the dynamic linker to quickly and unambiguously find the correct symbol. However, if the entry is marked as dynamic lookup [1], the dynamic linker will search all loaded images for the symbol and connect your library to the first one it finds. If the dynamic linker is unable to find a symbol, its default behaviour is to fail the load of the Mach-O image. This changes if the symbol is a weak reference. In that case, the dynamic linking continues to load the image but sets the address of the symbol to NULL. See Weak vs Weak vs Weak, below, for more about this. [1] In this case nm shows the library name as dynamically looked up. Weak vs Weak vs Weak Mach-O supports two different types of weak symbols: Weak references (aka weak imports) Weak definitions IMPORTANT If you use the term weak without qualification, the meaning depends on your audience. App developers tend to assume that you mean a weak reference whereas folks with a C++ background tend to assume that you mean a weak definition. It’s best to be specific. Weak References Weak references support the availability mechanism on Apple platforms. Most developers build their apps with the latest SDK and specify a deployment target, that is, the oldest OS version on which their app runs. Within the SDK, each declaration is annotated with the OS version that introduced that symbol [1]. If the app uses a symbol introduced later than its deployment target, the compiler flags that import as a weak reference. The app is then responsible for not using the symbol if it’s run on an OS release where it’s not available. For example, consider this snippet: #include <xpc/xpc.h> void testWeakReference(void) { printf("%p\n", xpc_listener_set_peer_code_signing_requirement); } The xpc_listener_set_peer_code_signing_requirement function is declared like so: API_AVAILABLE(macos(14.4)) … int xpc_listener_set_peer_code_signing_requirement(…); The API_AVAILABLE macro indicates that the symbol was introduced in macOS 14.4. If you build this code with the deployment target set to macOS 13, the symbol is marked as a weak reference: % nm -m Products/Debug/TestWeakRefC … (undefined) weak external _xpc_listener_set_peer_code_signing_requirement (from libSystem) If you run the above program on macOS 13, it’ll print NULL (actually 0x0). Without support for weak references, the dynamic linker on macOS 13 would fail to load the program because the _xpc_listener_set_peer_code_signing_requirement symbol is unavailable. [1] In practice most of the SDK’s declarations don’t have availability annotations because they were introduced before the minimum deployment target supported by that SDK. Weak definitions Weak references are about imports. Weak definitions are about exports. A weak definition allows you to export a symbol from multiple images. The dynamic linker coalesces these symbol definitions. Specifically: The first time it loads a library with a given weak definition, the dynamic linker makes it the primary. It registers that definition such that all references to the symbol resolve to it. This registration occurs in a namespace dedicated to weak definitions. That namespace is flat. Any subsequent definitions of that symbol are ignored. Weak definitions are weird, but they’re necessary to support C++’s One Definition Rule in a dynamically linked environment. IMPORTANT Weak definitions are not just weird, but also inefficient. Avoid them where you can. To flush out any unexpected weak definitions, pass the -warn_weak_exports option to the static linker. The easiest way to create a weak definition is with the weak attribute: __attribute__((weak)) void testWeakDefinition(void) { } IMPORTANT The C++ compiler can generate weak definitions without weak ever appearing in your code. This shows up in nm like so: % nm -m Products/Debug/TestWeakDefC … 0000000100003f40 (__TEXT,__text) weak external _testWeakDefinition … The output is quite subtle. A symbol flagged as weak external is either a weak reference or a weak definition depending on whether it’s undefined or not. For clarity, use dyld_info instead: % dyld_info -imports -exports Products/Debug/TestWeakRefC Products/Debug/TestWeakDefC [arm64]: … -imports: … 0x0001 _xpc_listener_set_peer_code_signing_requirement [weak-import] (from libSystem) % dyld_info -imports -exports Products/Debug/TestWeakDefC Products/Debug/TestWeakDefC [arm64]: -exports: offset symbol … 0x00003F40 _testWeakDefinition [weak-def] … … Here, weak-import indicates a weak reference and weak-def a weak definition. Weak Library There’s one final confusing use of the term weak, that is, weak libraries. A Mach-O image includes a list of imported libraries and a list of symbols along with the libraries they’re imported from. If an image references a library that’s not present, the dynamic linker will fail to load the library even if all the symbols it references in that library are weak references. To get around this you need to mark the library itself as weak. If you’re using Xcode it will often do this for your automatically. If it doesn’t, mark the library as optional in the Link Binary with Libraries build phase. Use otool to see whether a library is required or optional. For example, this shows an optional library: % otool -L Products/Debug/TestWeakRefC Products/Debug/TestWeakRefC: /usr/lib/libEndpointSecurity.dylib (… 511.60.5, weak) … In the non-optional case, there’s no weak indicator: % otool -L Products/Debug/TestWeakRefC Products/Debug/TestWeakRefC: /usr/lib/libEndpointSecurity.dylib (… 511.60.5) … Debug Symbols or Why the DWARF still stabs. (-: Historically, all debug information was stored in symbol table entries, using a format knows as stabs. This format is now obsolete, having been largely replaced by DWARF. However, stabs symbols are still used for some specific roles. Note See <mach-o/stab.h> and the stab man page for more about stabs on Apple platforms. See stabs and DWARF for general information about these formats. In DWARF, debug symbols aren’t stored in the symbol table. Rather, debug information is stored in various __DWARF sections. For example: % otool -l Intermediates.noindex/TestSymTab.build/Debug/TestSymTab.build/Objects-normal/arm64/TestCore.o | grep __DWARF -B 1 sectname __debug_abbrev segname __DWARF … The compiler inserts this debug information into the Mach-O object file that it creates. Eventually this Mach-O object file is linked into a Mach-O image. At that point one of two things happens, depending on the Debug Information Format build setting. During day-to-day development, set Debug Information Format to DWARF. When the linker creates a Mach-O image from a bunch of Mach-O object files, it doesn’t do anything with the DWARF information in those objects. Rather, it records references to the source objects files into the final image. This is super quick. When you debug that Mach-O image, the debugger finds those references and uses them to locate the DWARF information in the original Mach-O object files. Each reference is stored in a stabs OSO symbol table entry. To see them, run nm with the -a option: % nm -a Products/Debug/TestSymTab … 0000000000000000 - 00 0001 OSO …/Intermediates.noindex/TestSymTab.build/Debug/TestSymTab.build/Objects-normal/arm64/TestCore.o 0000000000000000 - 00 0001 OSO …/Intermediates.noindex/TestSymTab.build/Debug/TestSymTab.build/Objects-normal/arm64/main.o … Given the above, the debugger knows to look for DWARF information in TestCore.o and main.o. And notably, the executable does not contain any DWARF sections: % otool -l Products/Debug/TestSymTab | grep __DWARF -B 1 % When you build your app for distribution, set Debug Information Format to DWARF with dSYM File. The executable now contains no DWARF information: % otool -l Products/Release/TestSymTab | grep __DWARF -B 1 % Xcode runs dsymutil tool to collect the DWARF information, organise it, and export a .dSYM file. This is actually a document package, within which is a Mach-O dSYM companion file: % find Products/Release/TestSymTab.dSYM Products/Release/TestSymTab.dSYM Products/Release/TestSymTab.dSYM/Contents … Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab … % file Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab: Mach-O 64-bit dSYM companion file arm64 That file contains a copy of the the DWARF information from all the original Mach-O object files, optimised for use by the debugger: % otool -l Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab | grep __DWARF -B 1 … sectname __debug_line segname __DWARF … Raw Symbol Information As described above, each Mach-O file has a symbol table that’s an array of symbol table entries. The structure of each entry is defined by the declarations in <mach-o/nlist.h> [1]. While there is an nlist man page, the best documentation for this format is the the comments in the header itself. Note The terms nlist stands for name list and dates back to truly ancient versions of Unix. Each entry is represented by an nlist_64 structure (nlist for 32-bit Mach-O files) with five fields: n_strx ‘points’ to the string for this entry. n_type encodes the entry type. This is actually split up into four subfields, as discussed below. n_sect is the section number for this entry. n_desc is additional information. n_value is the address of the symbol. The four fields within n_type are N_STAB (3 bits), N_PEXT (1 bit), N_TYPE (3 bits), and N_EXT (1 bit). To see these raw values, run nm with the -x option: % nm -a -x Products/Debug/TestSymTab … 0000000000000000 01 00 0300 00000036 _getpid 0000000100003f44 24 01 0000 00000016 _main 0000000100003f44 0f 01 0000 00000016 _main … This prints a column for n_value, n_type, n_sect, n_desc, and n_strx. The last column is the string you get when you follow the ‘pointer’ in n_strx. The mechanism used to encode all the necessary info into these fields is both complex and arcane. For the details, see the comments in <mach-o/nlist.h> and <mach-o/stab.h>. However, just to give you a taste: The entry for getpid has an n_type field with just the N_EXT flag set, indicating that this is an external symbol. The n_sect field is 0, indicating a text symbol. And n_desc is 0x0300, with the top byte indicating that the symbol is imported from the third dynamic library. The first entry for _main has an n_type field set to N_FUN, indicating a stabs function symbol. The n_desc field is the line number, that is, line 22. The second entry for _main has an n_type field with N_TYPE set to N_SECT and the N_EXT flag set, indicating a symbol exported from a section. In this case the section number is 1, that is, the text section. [1] There is also an <nlist.h> header that defines an API that returns the symbol table. The difference between <nlist.h> and <mach-o/nlist.h> is that the former defines an API whereas the latter defines the Mach-O on-disk format. Don’t include both; that won’t end well!

Hello, We are experiencing slow launch time indicators in our performance monitoring tools(Crashlytics/DataDog/Xcode), and trying to understand what is the best approach to reduce it. Currently, cold launch takes ~900ms on iPhone 16 Pro , but ~2s on iPhone 11. Profiling app launch detected that most of the time is spend on loading the libraries. Our app is massive, we use a total of ~40 3rd parties libraries + 10 internal libraries. We enabled the "mergeable libraries" XCode new feature however the app launch is as written above. We also postponed some of the work in didFinishLaunch, which help a bit... But maybe we are trying to achieve the impossible? Could it be that large apps just can't reach the golden 500ms goal? Currently we are trying to create an "umbrella" library for all the third parties in order to force them to become part of the mergeable libraries. We would like to know if, are we on the right track?

In some recent releases of macos (14.x and 15.x), we have noticed what seems to be a slower dlopen() implementation. I don't have any numbers to support this theory. I happened to notice this "slowness" when investigating something unrelated. In one part of the code we have a call of the form: const char * fooBarLib = ....; dlopen(fooBarLib, RTLD_NOW + RTLD_GLOBAL); It so happened that due to some timing related issues, the process was crashing. A slow execution of code in this part of the code would trigger an issue in some other part of the code that would then lead to a process crash. The crash itself isn't a concern, because it's an internal issue that will addressed in the application code. What was interesting is that the slowness appears to be contributed by the call to dlopen(). Specifically, whenever a slowness was observed, the crash reports showed stack frames of the form: Thread 1: 0 dyld 0x18f08b5b4 _kernelrpc_mach_vm_protect_trap + 8 1 dyld 0x18f08f540 vm_protect + 52 2 dyld 0x18f0b87e0 lsl::MemoryManager::writeProtect(bool) + 204 3 dyld 0x18f0a7fe4 invocation function for block in dyld4::Loader::findAndRunAllInitializers(dyld4::RuntimeState&) const + 932 4 dyld 0x18f0e629c invocation function for block in dyld3::MachOAnalyzer::forEachInitializer(Diagnostics&, dyld3::MachOAnalyzer::VMAddrConverter const&, void (unsigned int) block_pointer, void const*) const + 172 5 dyld 0x18f0d9c38 invocation function for block in dyld3::MachOFile::forEachSection(void (dyld3::MachOFile::SectionInfo const&, bool, bool&) block_pointer) const + 496 6 dyld 0x18f08c2dc dyld3::MachOFile::forEachLoadCommand(Diagnostics&, void (load_command const*, bool&) block_pointer) const + 300 7 dyld 0x18f0d8bcc dyld3::MachOFile::forEachSection(void (dyld3::MachOFile::SectionInfo const&, bool, bool&) block_pointer) const + 192 8 dyld 0x18f0db5a0 dyld3::MachOFile::forEachInitializerPointerSection(Diagnostics&, void (unsigned int, unsigned int, bool&) block_pointer) const + 160 9 dyld 0x18f0e5f90 dyld3::MachOAnalyzer::forEachInitializer(Diagnostics&, dyld3::MachOAnalyzer::VMAddrConverter const&, void (unsigned int) block_pointer, void const*) const + 432 10 dyld 0x18f0a7bb4 dyld4::Loader::findAndRunAllInitializers(dyld4::RuntimeState&) const + 176 11 dyld 0x18f0af190 dyld4::JustInTimeLoader::runInitializers(dyld4::RuntimeState&) const + 36 12 dyld 0x18f0a8270 dyld4::Loader::runInitializersBottomUp(dyld4::RuntimeState&, dyld3::Array<dyld4::Loader const*>&, dyld3::Array<dyld4::Loader const*>&) const + 312 13 dyld 0x18f0ac560 dyld4::Loader::runInitializersBottomUpPlusUpwardLinks(dyld4::RuntimeState&) const::$_0::operator()() const + 180 14 dyld 0x18f0a8460 dyld4::Loader::runInitializersBottomUpPlusUpwardLinks(dyld4::RuntimeState&) const + 412 15 dyld 0x18f0c089c dyld4::APIs::dlopen_from(char const*, int, void*) + 2432 16 libjli.dylib 0x1025515b4 DoFooBar + 56 17 libjli.dylib 0x10254d2c0 Hello_World_Launch + 1160 18 helloworld 0x10250bbb4 main + 404 19 libjli.dylib 0x102552148 apple_main + 88 20 libsystem_pthread.dylib 0x18f4132e4 _pthread_start + 136 21 libsystem_pthread.dylib 0x18f40e0fc thread_start + 8 So, out of curiosity, have there been any known changes in the implementation of dlopen() which might explain the slowness? Like I noted, I don't have concrete numbers, but to quantify the slowness I don't think it's slower by a noticeable amount - maybe a few milli seconds. I guess what I am trying to understand is, whether there's anything that needs attention here.

Xcode 16.2 Flutter version 3.27.1 0 0x1008abee4 __assert_rtn + 160 1 0x1008add9c ld::tool::OutputFile::setFixup64(unsigned char*, unsigned long long, ld::Atom const*) (.cold.3) + 0 2 0x100789640 ld::tool::OutputFile::setFixup64(unsigned char*, unsigned long long, ld::Atom const*) + 656 3 0x100785b78 ld::tool::OutputFile::applyFixUps(ld::Internal&amp;, unsigned long long, ld::Atom const*, unsigned char*) + 4388 4 0x10078be18 ___ZN2ld4tool10OutputFile10writeAtomsERNS_8InternalEPh_block_invoke + 488 5 0x19bc19428 _dispatch_client_callout2 + 20 6 0x19bc2d850 _dispatch_apply_invoke3 + 336 7 0x19bc193e8 _dispatch_client_callout + 20 8 0x19bc1ac68 _dispatch_once_callout + 32 9 0x19bc2c8a4 _dispatch_apply_invoke + 252 10 0x19bc193e8 _dispatch_client_callout + 20 11 0x19bc2b080 _dispatch_root_queue_drain + 864 12 0x19bc2b6b8 _dispatch_worker_thread2 + 156 13 0x19bdc5fd0 _pthread_wqthread + 228 A linker snapshot was created at: /tmp/Test Kopi Kenangan.debug.dylib-2025-02-27-100512.ld-snapshot ld: Assertion failed: (reconstituted == accumulator), function setFixup64, file OutputFile.cpp, line 2975. clang: error: linker command failed with exit code 1 (use -v to see invocation)

Hi there I've recently had my upload rejected in Xcode Organizer as a result of one of the frameworks we use containing bitcode. Error: [ContentDelivery.Uploader.XXXXXXXXXX] Validation failed (409) Invalid Executable. The executable 'Sam.app/Frameworks/Foo.framework/Foo' contains bitcode. Is there an accurate way to determine whether an .xcframework contains bitcode ahead of time without using Xcode Organiser? My current methodology is below, please can I get some confirmation that this is accurate, or suggest a more efficient approach? I have concerns about my approach and whether it throws false positives for empty bitcode markers. 1. get original framework size 2. run xcrun bitcode_strip -r framework_path -o temp 3. get new framework size 4. if new size is smaller than original, then it contains bitcode Thanks for the help, Sam

Phenomenon We've found operator new/delete override in iOS app, only works for the first time when the app launches on iOS16, operator override is not working in the second and subsequent launch of the same app. Steps to reproduce Development environment: XCode 16.2 Create a new iOS Objective-C project in XCode In the project options page, choose the following settings: Name the project: OverrideNew Interface: Storyboard Language: Objective-C Testing System: None Add test code Change AppDelegate.m's file name to AppDelegate.mm to add the following C++ test code. Add the following code after #import "AppDelegate.h" #include &lt;os/log.h&gt; #include &lt;string&gt; static bool needLog = false; void* operator new(size_t size) { void* ptr = malloc(size); if(needLog) { // Log to prove override new works os_log_error(OS_LOG_DEFAULT, "Overrided new called. ptr: %p\n", ptr); } return ptr; } void operator delete(void* ptr) noexcept { free(ptr); if(needLog) { // Log to prove override delete works os_log_error(OS_LOG_DEFAULT, "Overrided delete called. ptr: %p\n", ptr); } } void StringConstructTest(void) { needLog = true; os_log_error(OS_LOG_DEFAULT, "Enter StringConstructTest1\n"); { std::string str; // a long string will trigger memory allocation on heap str = "Hello world and this is a long string.\n"; os_log_error(OS_LOG_DEFAULT, "%{public}s\n", str.c_str()); } os_log_error(OS_LOG_DEFAULT, "Exit StringConstructTest1\n"); needLog = false; } Call StringConstructTest() in didFinishLaunchingWithOptions method: - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. StringConstructTest(); return YES; } Change build settings Change Minimum Deployments: iOS 16. Build and run the project on an iOS16 device, emulator can not reproduce the problem. Observe logs in Console app on Mac Use the following log filters: message type: error process: OverrideNew First launch First launch on device(not from a XCode debug launch), the log is: Enter StringConstructTest1 Overrided new called. ptr: 0x281f2f450 Hello world and this is a long string. Overrided delete called. ptr: 0x281f2f450 Exit StringConstructTest1 "Overrided new called" proved the override new operator is called. Second and subsequence launch Second and subsequence launch on device(not from a XCode debug launch), the log is: Enter StringConstructTest1 Hello world and this is a long string. Exit StringConstructTest1 No log for "Overrided new called", the subsequence launch, the override operator new is not called anymore. Expected behavior For every app launch, log "Overrided new called" will happen and operator override works. On iOS16, operator override only works for the first launch. I've also tested on iOS18, operator override works every time as expected. Question Is there a way to force operator override works every time on iOS16?

I submitted feedback as FB16463501 -- posting here for others to see, or maybe for Apple to share any help if there are workarounds, etc.: Targets below iOS 18.x fail to launch app due to dyld[xxxxx]: Symbol not found: errors when referencing: MeshResource.init(from:) async - https://developer.apple.com/documentation/realitykit/meshresource/init(from:)-b7hb i.e. dyld[61511]: Symbol not found: _$s10RealityKit12MeshResourceC0A10FoundationE4fromACSayAD0C10DescriptorVG_tYaKcfC MeshResource.replace(with:) async - https://developer.apple.com/documentation/realitykit/meshresource/replace(with:)-8uvri i.e. dyld[78830]: Symbol not found: _$s10RealityKit12MeshResourceC0A10FoundationE7replace4withyAcDE8ContentsV_tYaKF Targets tested that exhibit issue: (DYLD errors) Device: iOS 17.7.2, iPhone 14 Pro Max Simulator: iOS 17.5 (21F79), iPhone 15 System Information: macOS Version 15.3 (Build 24D60) Xcode 16.2 (23507) (Build 16C5032a) MRE -- include this code in your app: (no need to invoke, just reference) static func addOrUpdateEntityModel_MRE(_ entity: ModelEntity) async { let descriptor = MeshDescriptor(name: "MyDescriptor") do { if let modelComponent = entity.model { // update existing ModelComponent if let model = try? MeshResource.Model(id: "MyModelId", descriptors: [descriptor]) { var contents = MeshResource.Contents() contents.models = .init([model]) try await modelComponent.mesh.replace(with: contents) /// `dyld[78830]: Symbol not found: _$s10RealityKit12MeshResourceC0A10FoundationE7replace4withyAcDE8ContentsV_tYaKF` } } else { //create new ModelComponent /// Comment-out the 2 lines below == dyld error for above `MeshResource.replace(with:)` let meshRes = try await MeshResource(from: [descriptor]) /// `dyld[61511]: Symbol not found: _$s10RealityKit12MeshResourceC0A10FoundationE4fromACSayAD0C10DescriptorVG_tYaKcfC` entity.model = .init(mesh: meshRes, materials: [SimpleMaterial()]) } } catch { fatalError() } }

One of the libraries that makes up my application depends on -undefined dynamic_lookup to link, and has since at least Snow Leopard if not earlier. I think iOS hasn't liked this for a while, but with the new linker I'm getting deprecation warnings even on OS X. I don't entirely understand what this flag does, other than it makes the build successful. :) So I'm at a loss on how to even approach fixing it. At this point, even links to useful resources would be appreciated, since googling hasn't yielded much beyond "remove -undefined to quiet the deprecation warning." FWIW, there is a bit of circular dependence between this library and another. On another OS, we need a carefully choreographed dance of building object files, then import libraries, then final linking to make this all work. So I suspect this may be related, but even if I'm correct, I don't know what would be the equivalent tools on Apple platforms.

I have developed framework and want to use this framework in authplugin which added on same project in different target That plugin target is working fine without framework, once I am adding framework the authplugin is not working Auth-plugin I am using to change in screen-saver plist

Hello Apple Team, I'm trying to import the Audodesk FBX SDK to my Objective-C iOS Project. The SDK is written in C++, but has support for iOS and the iOS simulator architectures. I've added the path to the include folder in the Header Search Path I've also added the paths to libfbxsdk.a in the Library Search Paths Finally, I've added the libfbxsdk.a file to the Link Binary with Libraries. However, when I build the project, I get the following error: building for 'iOS', but linking in object file (/Users/Lond/Documents/v2/Autodesk/iOS/2020.3.7/lib/ios/debug/libfbxsdk.a[28](fbxalloc.cxx.o)) built for 'macOS' In the terminal, if I type the command: 
lipo -info libfbxsdk.a I get the message Non-fat file: libfbxsdk.a is architecture: arm64 confirming that I'm using the library for the correct architecture.   Do I need to add any other confifuration option? (Like the other linker flag or something else) I'm quite new to C++, and integrating a C++ SDK into iOS is not easy.   I'm using Mac Os Sonoma 14.6.1 Tested on Xcode 15.4 and 16.2 Target Device: iPhone 13 Pro (iOS 17.6.1) iOS FBX SDK version: 2020.3.7 Link to the SDK if needed: https://aps.autodesk.com/developer/overview/fbx-sdk   Any help would be greatly appreciated Thank you

I'm currently facing a recurring issue while attempting to build my Flutter app for the iOS simulator. The build process fails with the following error Error (Xcode): Framework 'Flutter' not found Error (Xcode): Linker command failed with exit code 1 Steps I've Taken: Recreated the ios/ folder and cleared derived data: Used flutter clean to clean the project. Reinstalled CocoaPods with pod deintegrate followed by pod install. Verified Configuration: Checked AppDelegate and framework paths within Xcode. Set the deployment target to 14.0 in the Podfile. Additional Actions: Performed flutter clean again, followed by removal of Pods, .symlinks, and Flutter.framework under ios/. Updated CocoaPods, ensured all dependencies in pubspec.yaml are current. Added FirebaseCore initialization in AppDelegate.swift to resolve previous Firebase integration issues. Despite these efforts, the "Framework 'Flutter' not found" error persists. Here's the relevant part of my AppDelegate.swift and Podfile: swift import Flutter import UIKit @main @objc class AppDelegate: FlutterAppDelegate { override func application( _ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? ) -> Bool { GeneratedPluginRegistrant.register(with: self) return super.application(application, didFinishLaunchingWithOptions: launchOptions) } } ruby platform :ios, '14.0' CocoaPods analytics sends network stats synchronously affecting flutter build latency. ENV['COCOAPODS_DISABLE_STATS'] = 'true' project 'Runner', { 'Debug' => :debug, 'Profile' => :release, 'Release' => :release, } def flutter_root generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), FILE) unless File.exist?(generated_xcode_build_settings_path) raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first" end File.foreach(generated_xcode_build_settings_path) do |line| matches = line.match(/FLUTTER_ROOT=(.*)/) return matches[1].strip if matches end raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get" end require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root) flutter_ios_podfile_setup target 'Runner' do use_frameworks! use_modular_headers! flutter_install_all_ios_pods File.dirname(File.realpath(FILE)) target 'RunnerTests' do inherit! :search_paths end end post_install do |installer| installer.pods_project.targets.each do |target| flutter_additional_ios_build_settings(target) target.build_configurations.each do |config| xcconfig_path = config.base_configuration_reference.real_path xcconfig = File.read(xcconfig_path) xcconfig_mod = xcconfig.gsub(/DT_TOOLCHAIN_DIR/, "TOOLCHAIN_DIR") end end end Error Log from Flutter Run: [ +278 ms] Failed to build iOS app [ +42 ms] Error (Xcode): Framework 'Flutter' not found [ +8 ms] Error (Xcode): Linker command failed with exit code 1 (use -v to see invocation) [ +7 ms] Could not build the application for the simulator. [ +1 ms] Error launching application on iPhone 16 Pro Max. [ +6 ms] "flutter run" took 88,663ms. [ +164 ms] #0 throwToolExit (package:flutter_tools/src/base/common.dart:10:3) #1 RunCommand.runCommand (package:flutter_tools/src/commands/run.dart:860:9) #2 FlutterCommand.run. (package:flutter_tools/src/runner/flutter_command.dart:1450:27) #3 AppContext.run. (package:flutter_tools/src/base/context.dart:153:19) #4 CommandRunner.runCommand (package:args/command_runner.dart:212:13) #5 FlutterCommandRunner.runCommand. (package:flutter_tools/src/runner/flutter_command_runner.dart:421:9) #6 AppContext.run. (package:flutter_tools/src/base/context.dart:153:19) #7 FlutterCommandRunner.runCommand (package:flutter_tools/src/runner/flutter_command_runner.dart:364:5) #8 run.. (package:flutter_tools/runner.dart:131:9) #9 AppContext.run. (package:flutter_tools/src/base/context.dart:153:19) #10 main (package:flutter_tools/executable.dart:94:3) . Environment: Flutter: Version 3.27.3, Channel stable Xcode: Version 16.2, Build 16C5032a CocoaPods: Version 1.16.2 macOS: Version 15.2 (24C101) Additional Context: Initially, the issue was resolved by the sequence of cleanup and reinstalls listed above, but it re-emerged after integrating Firebase authentication. After adding FirebaseCore to AppDelegate.swift, the Firebase issue was resolved, but the framework error returned. I'm seeking guidance to resolve this issue permanently. Any insights or suggestions would be greatly appreciated!

Apologies that this is probably a simple problem. I've started from a sample code provided by Apple and changed it quite significantly. However, I'm not able to Archive the app. The original visionOS sample code has the same issue, so hopefully someone will be able to spot the problem: https://developer.apple.com/documentation/visionos/creating-stereoscopic-image-in-visionos The problems shown in the log are: Undefined symbol: _main Linker command failed with exit code 1 (use -v to see invocation) The first error seems to say that there's no "main" but there is indeed a @main in the EntryPoint.swift file. Any ideas? I have archived other apps (built from scratch) successfully, but clearly there's something different about this sample code. Many thanks!

We are considering the development of a new service, We would like to ask for detailed information on the feasibility of the following. Is it possible to encapsulate only xcframework, such as encapsulating xcframeworkA into xcframeworkB? If the above is possible, will the application incorporating the xcframework in the above state pass the review of apple?

Hi, I am trying to bring an existing Unity app to vision pro, and am trying to make all of the librairies compatible (the project loads native libs at runtime). For some of them, there is an arm64 IOS .framework file that seems to build and be found easily in the device, but for one of them I only got a .dylib. When building on xcode, it tells me it can't find it. So I added it to the lib search path in build settings, and it built. But on the device, it still can't seem to find the .dylib : Library not loaded: ./libpdfium.dylib Referenced from: <59B1ACCC-FFFD-3448-B03D-69AE95604C77> /private/var/containers/Bundle/Application/0606D884-CB09-44CA-8E4F-4A309D2E7053/[...].app/Frameworks/UnityFramework.framework/UnityFramework Reason: tried: '/usr/lib/system/introspection/libpdfium.dylib' (no such file, not in dyld cache), './libpdfium.dylib' (no such file), '/usr/lib/system/introspection/libpdfium.dylib' (no such file, not in dyld cache), '//libpdfium.dylib' (no such file) I am not used to Apple environment, is there a way to correctly reference this .dylib (not talking about compatibility here, just the first "lib found" step) ? Thanks.

Hi everyone, I’m encountering an issue with Firebase Dynamic Links in my app that I’m hoping someone can help me with. Everything was working perfectly before, but recently, I’ve run into a problem. Here’s the scenario: If the app is not installed and a Firebase Dynamic Link is clicked, the user is correctly redirected to the app store to install the app. Once the app is installed and opened for the first time, the dynamic link doesn't work. The app doesn't open to the correct content or link that was clicked. I’ve tried the following troubleshooting steps with no success: Verified that the app is configured properly in Firebase and that the Dynamic Links settings are correct. Checked the app's deep linking settings and ensured everything matches with the Firebase setup. Confirmed that the Firebase SDK is up-to-date. Attempted to clear app cache and reinstall. Tested the links in both debug and production modes. Despite trying all these steps, the issue persists. Has anyone else faced this issue before or have any suggestions for how to fix it? Any insights would be greatly appreciated! Thanks in advance!

I created a new iOS project (storyboard if it matters) and added a bunch of C files to it. Some portion of the C files depend on libcurl. I would like to be able to build for both simulator and device if possible. Google claims that Xcode can provide the dependency as part of the inbuilt libraries however I do not see libcurl.4.tbd (or any version) as an option to choose. Is this feature no longer available or is there something I am missing here? For context here is a screen shot of my build error situation

We have a relatively big iOS-only project with around 80 build targets from swift packages (local features and external project dependencies) and Xcode 15.4 (originally, migrated to 16.0). Project compiles and runs great, but xcodebuild archive will fail 4 out of 5 tries with this: ld: file cannot be open()ed, errno=2 path=/opt/builds/fLLyxmhG/0/myapp/Build/Intermediates.noindex/ArchiveIntermediates/myapp (Development Flow)/BuildProductsPath/Debug-iphonesimulator/Account.o in '/opt/builds/fLLyxmhG/0/myapp/Build/Intermediates.noindex/ArchiveIntermediates/myapp (Development Flow)/BuildProductsPath/Debug-iphonesimulator/Account.o' Where Account.o is an end product of one of our feature packages linking to an .app itself. This error is not tied to this concrete package/product (which should be compiling almost last relative to build graph) and could appear mid-build in between our service layer packages. It seems (and is approved by Xcode timeline for .app archive log) that module dependency is compiled later than module itself and linker just cant find its dependency object files. The scheme is: Module A (dependency itself) Module B (needs module A) And with build order expected (???) to be A (first) -> B we're getting the B -> A. Error appears only when archiving for Debug configuration, archiving the same end-target with Release configuration results in stable passes 10 out of 10 tries. Setting identical parameters in Build Settings tab for both configurations of a target is not giving any effect. Our current fix is choosing Manual order in scheme Build order setting. Everything works as expected, but i guess it's not optimal 🤧 Sadly can't provide test project, but anything else — welcome.

The customer's iPhone 13 Pro Max crashes when opening the app after upgrading to iOS 18.1.1. The crash information collected via TestFlight is as follows:

I am working on adding Objective-C ABI support to DLang and currently I'm getting the following error when linking with ld. Assertion failed: (fixups().size() == 1), function classTarget I'm curious as to why I am getting this error, looking at the objective-c runtime source, i have not applied any of the fixup flags to any protocol definitions. From my understanding, the source of the linker is not available so it's a bit on the difficult side to determine which part is wrong. The source of my pull-request is available here: https://github.com/ldc-developers/ldc/pull/4777

Undefined symbol: OBJC_CLASS$_ADClient The ADClient used in the project has been removed, but Xcode16.1 still reports this error.